U.S. patent number 4,959,436 [Application Number 07/212,279] was granted by the patent office on 1990-09-25 for narrow mwd alpha-olefin copolymers.
This patent grant is currently assigned to Exxon Research and Engineering Co.. Invention is credited to Charles Cozewith, Shiaw Ju, Gary W. Verstrate.
United States Patent |
4,959,436 |
Cozewith , et al. |
* September 25, 1990 |
Narrow MWD alpha-olefin copolymers
Abstract
The present invention relates to novel copolymers of
alpha-olefins comprised of intramolecularly heterogeneous and
intermolecularly homogeneous copolymer chains.
Inventors: |
Cozewith; Charles (Westfield,
NJ), Ju; Shiaw (Edison, NJ), Verstrate; Gary W.
(Matawan, NJ) |
Assignee: |
Exxon Research and Engineering
Co. (Florham Park, NJ)
|
[*] Notice: |
The portion of the term of this patent
subsequent to December 20, 2005 has been disclaimed. |
Family
ID: |
27395718 |
Appl.
No.: |
07/212,279 |
Filed: |
June 27, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
745873 |
Jun 17, 1985 |
4792595 |
|
|
|
504582 |
Jun 15, 1983 |
4540753 |
|
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Current U.S.
Class: |
526/348;
525/331.7; 526/348.3; 526/348.4; 526/348.6; 525/323; 526/348.2;
526/348.5; 526/348.7 |
Current CPC
Class: |
C08F
210/18 (20130101); C08F 210/02 (20130101); C08F
297/08 (20130101); C10M 143/00 (20130101); C08F
210/16 (20130101); C08F 210/02 (20130101); C08F
4/68 (20130101); C10M 2205/00 (20130101); C10M
2205/08 (20130101); C10M 2205/02 (20130101); B01J
2219/00099 (20130101); B01J 2219/00186 (20130101); C10M
2205/022 (20130101); B01J 2219/00159 (20130101); C10N
2020/01 (20200501); C10M 2205/10 (20130101); C08F
210/16 (20130101); C08F 210/06 (20130101); C08F
2500/03 (20130101); C08F 2500/06 (20130101); C08F
210/18 (20130101); C08F 210/06 (20130101); C08F
2500/25 (20130101); C08F 2500/03 (20130101); C08F
2500/06 (20130101) |
Current International
Class: |
C10M
143/00 (20060101); C08F 297/00 (20060101); C08F
297/08 (20060101); C08F 210/02 (20060101); C08F
210/00 (20060101); C08F 210/16 (20060101); C08F
210/18 (20060101); C08F 010/00 () |
Field of
Search: |
;526/348,348.2,348.3,348.4,348.5,348.6,348.7 ;525/323,331.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Cazes, J. Editor, "Liquid Chromotography of Polymers and Related
Materials III" Marcel Dekker, 1981, On Line Determination by Light
Scattering of Mechanical Degradation in the GPC Process, Rooney, J.
G. & VerStrate, G., p. 207. .
H. Inagaki and T. Tanaku, Developments in Polymer Characterization,
vol. 3, 1 (1982). .
1981 MMI International Symposium on "Transition Metal Catalyzed
Polymerzations", Unsolved Problems. .
Makromol. Chem., Rapid Commun. 3, 225-229 (1982), DOI, Y. Yeki S.,
Block Copolymerization of Propylene and Ethylene with the "Living".
. . .
C. K. Shih, Transactions of the Society of Rheology, vol. 14, "The
Effect of Molecular Weight and Molecular Weight Distribution on the
Non-Newtonian Behavior of Ethylene-Propylene-Diene Polymers," John
Wiley & Sons Inc. (1970), pp. 83-114. .
C. Cozewith and G. VerStrate, Macromolecules, vol. 4,
"Ethylene-Propylene Copolymers, Reactivity Ratios, Evaluation, and
Significance," (1971) pp. 482-489. .
M. Cantow, Editor, Academic, "Polymer Fractionation", (1967), p.
341 ff. .
E. Junghanns, A. Gumboldt, and G. Bier, Makromol. Chem., vol. 58,
"Polymerization of Ethylene and Propylene to Amorphous Copolymers
with Catalysts of Vanadium Oxychloride and Alkyl Aluminum Halides,"
(1962), pp. 18-42. .
J. F. Wehner, Chemical Reaction Engineering-Houston, "Laminar Flow
Polymerization of EPDM Polymer" ACS Symposium Series 65 (1978), pp.
140-152. .
Yutaka Mitsuda, John L. Schrag, and John D. Ferry, Journal of
Applied Polymer Science, vol. 18, "Estimation of Long-Chain
Branching in Ethylene-Propylene Terpolymers from Infinite-Dilution
Viscoelastic Properties," John Wiley & Sons Inc. (1974) pp.
193-202..
|
Primary Examiner: Schofer; Joseph L.
Assistant Examiner: Mulcahy; Peter D.
Attorney, Agent or Firm: Muller; W. G.
Parent Case Text
RELATED APPLICATION DATA
This application is a continuation of application Ser. No. 745,873,
filed June 17, 1985, now U.S. Pat. No. 4,792,595, which is a
divisional of application Ser. No. 504,582, filed June 15, 1983,
issued as U.S. Pat. No. 4,540,753 on Sept. 10, 1985.
Claims
What is claimed is:
1. Copolymer of ethylene and at least one other alpha-olefin
monomer, said copolymer having an average ethylene composition and
comprising intramolecularly hetergeneous copolymer chains wherein
at least two portions of an individual intramolecularly
hetergeneous chain, each portion comprising at least 5 weight
percent of said chain, differ in composition from one another by at
least 5 weight percent ethylene, wherein said copolymer has an
intermolecular compositional dispersity such that 95 weight percent
of said copolymer chains have a composition 15 weight percent or
less different from said average ethylene composition, and wherein
said copolymer has a weight average molecular weight of from about
2,000 to about 12,000,000, and a MWD characterized by at least one
of a ratio of M.sub.w /M.sub.n of less than 2 and a ratio of
M.sub.z /M.sub.w of less than 1.8.
2. A copolymer according to claim 1, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition.
3. A copolymer according to claim 1, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition.
4. A copolymer according to claim 1, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 10 weight percent ethylene.
5. A copolymer according to claim 1, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 20 weight percent ethylene.
6. A copolymer according to claim 1, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
7. A copolymer according to claim 1, which has a MWD characterized
by both a ratio of M.sub.w /M.sub.n of less than about 1.6 and a
ratio of M.sub.z /M.sub.w of less than about 1.5.
8. A copolymer according to claim 1, which has a MWD characterized
by at least one of a ratio of M.sub.w /M.sub.n of less than about
1.6 and a ratio of M.sub.z /M.sub.w of less than about 1.5.
9. A copolymer according to claim 8, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 10 weight percent ethylene.
10. A copolymer according to claim 9 which is comprised of
ethylene, propylene and ENB.
11. A copolymer according to claim 9 which is cured.
12. A copolymer according to claim 9, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
13. A copolymer according to claim 1, which has a MWD characterized
by at least one of a ratio of M.sub.w /M.sub.n of less than about
1.4 and a ratio of M.sub.z /M.sub.w of less than about 1.3.
14. A copolymer according to claim 13, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 20 weight percent ethylene.
15. A copolymer according to claim 14, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
16. A copolymer according to claim 1 which has a MWD characterized
by both of a ratio of M.sub.w /M.sub.n of less than about 1.4 and a
ratio of M.sub.z /M.sub.w of less than about 1.3.
17. A copolymer according to claim 1, having a total maximum
ethylene content of about 85% on a weight basis.
18. A copolymer according to claim 1, having a total maximum
ethylene content of about 90% on a weight basis.
19. A copolymer according to claim 18, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition.
20. A copolymer according to claim 18, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition.
21. A copolymer according to claim 18, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 10 weight percent ethylene.
22. A copolymer according to claim 18, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 20 weight percent ethylene.
23. A copolymer according to claim 18, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
24. A copolymer according to claim 18, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.6 and a ratio of M.sub.z /M.sub.w of less than
about 1.5.
25. A copolymer according to claim 24, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 10 weight percent ethylene.
26. A copolymer according to claim 25, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
27. A copolymer according to claim 25, further comprising
diene.
28. A copolymer according to claim 27, wherein the total ethylene
content if about 30% to 75% on a weight basis.
29. A copolymer according to claim 18, which has a MWD
characterized by both a ratio of M.sub.w /M.sub.n of less than
about 1.6 and a ratio of M.sub.z /M.sub.w of less than about
1.5.
30. A copolymer according to claim 18, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.4 and a ratio of M.sub.z /M.sub.w of less than
about 1.3.
31. A copolymer according to claim 20, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 20 weight percent ethylene.
32. A copolymer according to claim 31, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
33. A copolymer according to claim 18, which has a MWD
characterized by both of a ratio of M.sub.w /M.sub.n of less than
about 1.4. and a ratio of M.sub.z /M.sub.w of less than about
1.3.
34. A copolymer according to claim 1, having a total ethylene
content of greater than about 25% on a weight basis.
35. A copolymer according to claim 1, further comprising diene.
36. A copolymer according to claim 1 which is cured.
37. A copolymer according to claim 1 which has a weight average
molecular weight of about 10,000 to 1,000,000.
38. A copolymer according to claim 1, which has a weight average
molecular weight of about 20,000 to 750,000.
39. Copolymer of ethylene and at least one other alpha-olefin
monomer, said copolymer having an average ethylene composition and
comprising intramolecularly hetergeneous copolymer chains wherein
at least two portions of an individual intramolecularly
hetergeneous chain, each portion comprising at least 5 weight
percent of said chain, differ in composition from one another by at
least 5 weight percent ethylene, wherein said substantially all
said portions contain ethylene, wherein said copolymer has an
intermolecular compositional dispersity such that 95 weight percent
of said copolymer chains have a composition 15 weight percent or
less different from said average ethylene composition, and wherein
said copolymer has a MWD characterized by at least one of a ratio
of M.sub.w /M.sub.n of less than 2 and a ratio of M.sub.z /M.sub.w
of less than 1.8, and wherein said copolymer has a weight average
molecular weight of from about 15,000 to about 12,000,000.
40. A copolymer according to claim 39, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition.
41. A copolymer according to claim 29, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition.
42. A copolymer according to claim 29, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 10 weight percent ethylene.
43. A copolymer according to claim 40, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 20 weight percent ethylene.
44. A copolymer according to claim 39, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
45. A copolymer according to claim 39, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.6 and a ratio of M.sub.z /M.sub.w of less than
about 1.5.
46. A copolymer according to claim 45, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 10 weight percent ethylene.
47. A copolymer according to claim 46, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
48. A copolymer according to claim 46, which is comprised of
ethylene, propylene and ENB.
49. A copolymer according to claim 46 which is cured.
50. A copolymer according to claim 39, which has a MWD
characterized by both a ratio of M.sub.w /M.sub.n of less than
about 1.6 and a ratio of M.sub.z /M.sub.w of less than 1.5.
51. A copolymer according to claim 39, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.4 and a ratio of M.sub.z /M.sub.w of less than
about 1.3.
52. A copolymer according to claim 51, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 20 weight percent ethylene.
53. A copolymer according to claim 52, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
54. A copolymer according to claim 39, which has a MWD
characterized by both of a ratio of M.sub.w /M.sub.n of less than
about 1.4 and a ratio of M.sub.z /M.sub.w of less than about
1.3.
55. A copolymer according to claim 39, having a total maximum
ethylene content of about 90% on a weight basis.
56. A copolymer according to claim 55, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition.
57. A copolymer according to claim 55, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition.
58. A copolymer according to claim 55, wherein said at least two
portions of an individual chain differ in composition from one
another by least 10 weight percent ethylene.
59. A copolymer according to claim 55, wherein said at least two
portions of an individual chain differ in composition from one
another by least 20 weight percent ethylene.
60. A copolymer according to claim 55, wherein said at least two
portions of an individual chain differ in composition from one
another by least 40 weight percent ethylene.
61. A copolymer according to claim 55, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.6 and a ratio of M.sub.z /M.sub.w of less than
about 1.5.
62. A copolymer according to claim 61, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 13% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 10 weight percent ethylene.
63. A copolymer according to claim 62, wherein said at least two
portions of an individual chain differ in composition from one
another by least 40 weight percent ethylene.
64. A copolymer according to claim 62, further comprising
diene.
65. A copolymer according to claim 64, wherein the total ethylene
content is about 30% to 75% on a weight basis.
66. A copolymer according to claim 55, which has a MWD
characterized by both a ratio of M.sub.w /M.sub.n of less than
about 1.6 and a ratio of M.sub.z /M.sub.w of less than about
1.5.
67. A copolymer according to claim 55, which has a MWD
characterized by at least one of a ratio of M.sub.w /M.sub.n of
less than about 1.4 and a ratio of M.sub.z /M.sub.w of less than
about 1.3.
68. A copolymer according to claim 67, wherein said intermolecular
compositional dispersity of said copolymer is such that 95 weight
percent of said copolymer chains have a composition 10% or less
different from said average ethylene composition, and wherein said
at least two portions of an individual chain differ in composition
from one another by at least 20 weight percent ethylene.
69. A copolymer according to claim 68, wherein said at least two
portions of an individual chain differ in composition from one
another by at least 40 weight percent ethylene.
70. A copolymer according to claim 55, which has a MWD
characterized by both a ratio of M.sub.w /M.sub.n of less than
about 1.4 and a ratio of M.sub.z /M.sub.w of less than about
1.3.
71. A copolymer according to claim 39, having a total maximum
ethylene content of about 85% on a weight basis.
72. A copolymer according to claim 39, having a total ethylene
content of greater than about 25% on a weight basis.
73. A copolymer according to claim 39, further comprising
diene.
74. A copolymer according to claim 39 which is cured.
75. A copolymer according to claim 39, which has a weight average
molecular weight of about 15,000 to 12,000,000.
76. A copolymer according to claim 39, which has a weight average
molecular weight of about 15,000 to 12,000,000.
77. A copolymer according to claim 39, which has a weight average
molecular weight of about 20,000 to 750,000.
78. A copolymer according to claim 39, wherein said copolymer was
formed by a polymerization conducted:
(a) in at least one mix-free reactor,
(b) with essentially one active catalyst species,
(c) using at least one reaction mixture which is essentially
transfer agent-free, and which comprises ethylene at the initiation
of said polymerization, and
(d) in such a manner and under conditions sufficient to initiate
propagation of essentially all copolymer chains simultaneously.
79. A copolymer according to claim 78, wherein said catalyst
comprises hydrocarbon-soluble vanadium compound and organo-aluminum
compound which react to form essentially one active catalyst
species, at least one of the vanadium compound and organo-aluminum
compound containing a valence-bonded halogen.
80. A copolymer according to claim 79, wherein said polymerization
reaction is continuous and is conducted in hexane solvent.
81. A copolymer according to claim 79, wherein said catalyst
comprises:
(a) hydrocarbon-soluble vanadium compound selected from the group
consisting of: ##STR3## where x=0-3 and R=hydrocarbon radical;
VCl.sub.4 ;
VO(AcAc).sub.2, where AcAc=acetyl acetonate;
VOCl.sub.x (AcAc).sub.3-x, where x=1 or 2 and AcAc=acetyl
acetonate; and
VCl.sub.3.nB, where n=2-3 and B=Lewis base capable of forming
hydrocarbon-soluble complexes with VCl.sub.3 ; and
(b) organo-aluminum compound selected from the group consisting
of:
AlR.sub.3 ;
AlR.sub.2 Cl;
Al.sub.2 R.sub.3 Cl.sub.3 ;
AlRCl.sub.2 ;
AlR'RCl;
Al(OR')R.sub.2 ;
R.sub.2 Al--OAlR.sub.2 ; and
AlR.sub.2 I;
where R and R.sup.1 are hydrocarbon radicals.
82. A copolymer according to claim 81, wherein said catalyst
comprises VCl.sub.4 and Al.sub.2 R.sub.3 Cl.sub.3.
83. A copolymer according to claim 78, wherein said polymerization
is conducted in at least one tubular reactor.
84. A copolymer according to claim 83, wherein said reaction
mixture further comprises diene, and wherein at least one of said
ethylene, other alpha-olefin monomer and diene are fed to said
tubular reactor at multiple feed sites.
Description
BACKGROUND OF THE INVENTION
The present invention relates to novel copolymers of alpha-olefins.
More specifically, it relates to novel copolymers of ethylene with
other alpha-olefins comprised of copolymer chains with compositions
which are intramolecularly heterogeneous and intermolecularly
homogeneous, as well as, to a process for making these copolymers
and their use in lube oil and elastomer applications.
For convenience, certain terms that are repeated throughout the
present specification are defined below:
a. Inter-CD defines the compositional variation, in terms of
ethylene content, among polymer chains. It is expressed as the
minimum deviation (analogous to a standard deviation) in terms of
weight percent ethylene from the average ethylene composition for a
given copolymer sample needed to include a given weight percent of
the total co-polymer sample which is obtained by excluding equal
weight fractions from both ends of the distribution. The deviation
need not be symmetrical. When expressed as a single number for
example 15% Inter-CD, it shall mean the larger of the positive or
negative deviations. For example, for a Gaussian compositional
distribution, 95.5% of the polymer is within 20 wt. % ethylene of
the mean if the standard deviation is 10%. The Inter-CD for 95.5
wt. % of the polymer is 20 wt. % ethylene for such a sample.
b. Intra-CD is the compositional variation, in terms of ethylene,
within a copolymer chain. It is expressed as the minimum difference
in weight (wt.) % ethylene that exists between two portions of a
single copolymer chain, each portion comprising at least 5 weight %
of the chain.
c. Molecular weight distribution (MWD) is a measure of the range of
molecular weights within a given copolymer sample. It is
characterized in terms of at least one of the ratios of weight
average to number average molecular weight, M.sub.w /M.sub.n, and Z
average to weight average molecular weight, M.sub.z /M.sub.w,
where: ##EQU1## Ni is the number of molecules of weight Mi.
d. Viscosity Index (V.I.) is the ability of a lubricating oil to
accommodate increases in temperature with a minimum decrease in
viscosity. The greater this ability, the higher the V.I.
Ethylene-propylene copolymers, particularly elastomers, are
important commercial products. Two basic types of
ethylene-propylene copolymers are commercially available.
Ethylene-propylene copolymers (EPM) are saturated compounds
requiring vulcanization with free radical generators such as
organic peroxides. Ethylene-propylene terpolymers (EPDM) contain a
small amount of non-conjugated diolefin, such as dicyclopentadiene;
1,4-hexadiene or ethylidene norbornene, which provides sufficient
unsaturation to permit vulcanization with sulfur. Such polymers
that include at least two monomers, i.e., EPM and EPDM, will
hereinafter be collectively referred to as copolymers.
These copolymers have outstanding resistance to weathering, good
heat aging properties and the ability to be compounded with large
quantities of fillers and plasticizers resulting in low cost
compounds which are particularly useful in automotive and
industrial mechanical goods applications. Typical automotive uses
are tire sidewalls, inner tubes, radiator and heater hose, vacuum
tubing, weather stripping and sponge doorseals and Viscosity Index
(V.I.) improvers for lubricating oil compositions. Typical
mechanical goods uses are for appliance, industrial and garden
hoses, both molded and extruded sponge parts, gaskets and seals and
conveyor belt covers. These copolymers also find use in adhesives,
appliance parts as in hoses and gaskets, wire and cable and
plastics blending.
As can be seen from the above, based on their respective
properties, EPM and EPDM find many, varied uses. It is known that
the properties of such copolymers which make them useful in a
particular application are, in turn, determined by their
composition and structure. For example, the ultimate properties of
an EPM or EPDM copolymer are determined by such factors as
composition, compositional distribution, sequence distribution,
molecular weight, and molecular weight distribution (MWD).
The efficiency of peroxide curing depends on composition. As the
ethylene level increases, it can be shown that the "chemical"
crosslinks per peroxide molecule increases. Ethylene content also
influences the rheological and processing properties, because
crystallinity, which acts as physical crosslinks, can be
introduced. The crystallinity present at very high ethylene
contents may hinder processibility and may make the cured product
too "hard" at temperatures below the crystalline melting point to
be useful as a rubber.
Milling behavior of EPM or EPDM copolymers varies radically with
MWD. Narrow MWD copolymers crumble on a mill, whereas broad MWD
materials will band under conditions encountered in normal
processing operations. At the shear rates encountered in processing
equipment, broader MWD copolymer has a substantially lower
viscosity than narrower MWD polymer of the same weight average
molecular weight or low strain rate viscosity.
Thus, there exists a continuing need for discovering polymers with
unique properties and compositions. This is easily exemplified with
reference to the area of V.I. improvers for lubricating oils.
A motor oil should not be too viscous at low temperatures so as to
avoid serious frictional losses, facilitate cold starting and
provide free oil circulation right from engine startup. On the
other hand, it should not be too thin at working temperatures so as
to avoid excessive engine wear and excessive oil consumption. It is
most desirable to employ a lubricating oil which experiences the
least viscosity-change with changes in temperature.
The ability of a lubricating oil to accommodate increases in
temperature with a minimum decrease in viscosity is indicated by
its Viscosity Index (V.I.). The greater this ability, the higher
the V.I.
Polymeric additives have been extensively used in lubricating oil
compositions to impart desirable viscosity-temperature
characteristics to the compositions. For example, lubricating oil
compositions which use EPM or EPDM copolymers or, more generally,
ethylene-(C.sub.3 -C.sub.18) alpha-olefin copolymers, as V.I.
improvers are well known. These additives are designed to modify
the lubricating oil so that changes in viscosity occurring with
variations in temperature are kept as small as possible.
Lubricating oils containing such polymeric additives essentially
maintain their viscosity at higher temperatures while at the same
time maintaining desirable low viscosity fluidity at engine
starting temperatures.
Two important properties (although not the only required properties
as is known) of these additives relate to low temperature
performance and shear stability. Low temperature performance
relates to maintaining low viscosity at very low temperatures,
while shear stability relates to the resistance of the polymeric
additives to being broken down into smaller chains.
The present invention is drawn to a novel copolymer of ethylene and
at least one other alpha-olefin monomer which copolymer is
intramolecularly heterogeneous and intermolecularly homogeneous.
Furthermore, the MWD of the copolymer is very narrow. It is well
known that the breadth of the MWD can be characterized by the
ratios of various molecular weight averages. For example, an
indication of a narrow MWD in accordance with the present invention
is that the ratio of weight to number average molecular weight
(M.sub.w /M.sub.n) is less than 2. Alternatively, a ratio of the
Z-average molecular weight to the weight average molecular weight
(M.sub.z /M.sub.w) of less than 1.8 typifies a narrow MWD in
accordance with the present invention. It is known that the
property advantages of copolymers in accordance with the present
invention are related to these ratios. Small weight fractions of
material can disproportionately influence these ratios while not
significantly altering the property advantages which depend on
them. For instance, the presence of a small weight fraction (e.g.
2%) of low molecular weight copolymer can depress M.sub.n, and
thereby raise M.sub.w /M.sub.n above 2 while maintaining M.sub.z
/M.sub.w less than 1.8. Therefore, polymers, in accordance with the
present invention, are characterized by having at least one of
M.sub.w /M.sub.n less than 2 and M.sub.z /M.sub.w less than 1.8.
The copolymer comprises chains within which the ratio of the
monomers varies along the chain length. To obtain the
intramolecular compositional heterogeneity and narrow MWD, the
copolymers in accordance with the present invention are preferably
made in a tubular reactor. It has been discovered that to produce
such copolymers requires the use of numerous heretofore undisclosed
method steps conducted within heretofore undisclosed preferred
ranges. Accordingly, the present invention is also drawn to a
method for making the novel copolymers of the present
invention.
Copolymers in accordance with the present invention have been found
to have improved properties in lubricating oil. Accordingly, the
present invention is also drawn to a novel oil additive composition
which comprises basestock mineral oil of lubricating viscosity
containing an effective amount of a viscosity index improver being
copolymer in accordance with the present invention.
DESCRIPTION OF THE PRIOR ART
Representative prior art dealing with tubular reactors to make
copolymers are as follows:
In "Polymerization of ethylene and propylene to amorphous
copolymers with catalysts of vanadium oxychloride and alkyl
aluminum halides"; E. Junghanns, A. Gumboldt and G. Bier; Makromol.
Chem., v. 58 (12/12/62): 18-42, the use of a tubular reactor to
produce ethylene-propylene copolymer is disclosed in which the
composition varies along the chain length. More specifically, this
reference discloses the production in a tubular reactor of
amorphous ethylene-propylene copolymers using Ziegler catalysts
prepared from vanadium compound and aluminum alkyl. It is disclosed
that at the beginning of the tube ethylene is preferentially
polymerized, and if no additional make-up of the monomer mixture is
made during the polymerization the concentration of monomers
changes in favor of propylene along the tube. It is further
disclosed that since these changes in concentrations take place
during chain propagation, copolymer chains are produced which
contain more ethylene on one end than at the other end. It is also
disclosed that copolymers made in a tube are chemically
non-uniform, but fairly uniform as regards molecular weight
distribution. Using the data reported in their FIG. 17 for
copolymer prepared in the tube, it was estimated that the M.sub.w
/M.sub.n ratio for this copolymer was 1.6, and from their FIG. 18
that the intermolecular compositional dispersity (Inter-CD,
explained in detail below) of this copolymer was greater than
15%.
"Laminar Flow Polymerization of EPDM Polymer"; J. F. Wehner; ACS
Symposium Series 65 (1978); pp 140-152 discloses the results of
computer simulation work undertaken to determine the effect of
tubular reactor solution polymerization with Ziegler catalysts on
the molecular weight distribution of the polymer product. The
specific polymer simulated was an elastomeric terpolymer of
ethylene-propylene-1,4-hexadiene. On page 149, it is stated that
since the monomers have different reactivities, a polymer of
varying composition is obtained as the monomers are depleted.
However, whether the composition varies inter-or intramolecularly
is not distinguished. In Table III on page 148, various polymers
having M.sub.w /M.sub.n of about 1.3 are predicted. In the third
paragraph on page 144, it is stated that as the tube diameter
increases, the polymer molecular weight is too low to be of
practical interest, and it is predicted that the reactor will plug.
It is implied in the first paragraph on page 149 that the
compositional dispersity produced in a tube would be detrimental to
product quality.
U.S. Pat. No. 3,681,306 to Wehner is drawn to a process for
producing ethylene/higher alpha-olefin copolymers having good
processability, by polymerization in at least two consecutive
reactor stages. According to this reference, this two-stage process
provides a simple polymerization process that permits tailor-making
ethylene/alpha-olefin copolymers having predetermined properties,
particularly those contributing to processability in commercial
applications such as cold-flow, high green strength and
millability. According to this reference, the inventive process is
particularly adapted for producing elastomeric copolymers, such as
ethylene/propylene/5-ethylidene-2-norbornene, using any of the
coordination catalysts useful for making EPDM. The preferred
process uses one tubular reactor followed by one pot reactor.
However, it is also disclosed that one tubular reactor could be
used, but operated at different reaction conditions to simulate two
stages. As is seen from column 2, lines 14-20, the inventive
process makes polymers of broader MWD than those made in a single
stage reactor. Although intermediate polymer from the first
(pipeline) reactor is disclosed as having a ratio of M.sub.w
/M.sub.n of about 2, as disclosed in column 5, lines 54-57, the
final polymers produced by the inventive process have an M.sub.w
/M.sub.n of 2.4 to 5.
U.S. Pat. No. 3,625,658 to Closon discloses a closed circuit
tubular reactor apparatus with high recirculation rates of the
reactants which can be used to make elastomers of ethylene and
propylene. With particular reference to FIG. 1, a hinged support 10
for vertical leg 1 of the reactor allows for horizontal expansion
of the bottom leg thereof and prevents harmful deformations due to
thermal expansions, particularly those experienced during reactor
clean out.
U.S. Pat. No. 4,065,520 to Bailey et al discloses the use of a
batch reactor to make ethylene copolymers, including elastomers,
having broad compositional distributions. Several feed tanks for
the reactor are arranged in series, with the feed to each being
varied to make the polymer. The products made have crystalline to
semi-crystalline to amorphous regions and gradient changes in
between. The catalyst system can use vanadium compounds alone or in
combination with titanium compound and is exemplified by vanadium
oxy-trichloride and diisobutyl aluminum chloride. In all examples
titanium compounds are used. In several examples hydrogen and
diethyl zinc, known transfer agents, are used. The polymer chains
produced have a compositionally disperse first length and uniform
second length. Subsequent lengths have various other compositional
distributions.
In "Estimation of Long-Chain Branching in Ethylene-Propylene
Terpolymers from Infinite-Dilution Viscoelastic Properties"; Y.
Mitsuda, J. Schrag, and. J. Ferry; J. Appl. Pol Sci., 18, 193
(1974) narrow MWD copolymers of ethylene-propylene are disclosed.
For example, in TABLE II on page 198, EPDM copolymers are disclosed
which have M.sub.w /M.sub.n of from 1.19 to 1.32.
In "The Effect of Molecular Weight and Molecular Weight
Distribution on the Non-Newtonian Behavior of
Ethylene-Propylene-Diene Polymers; Trans. Soc. Rheol., 14, 83
(1970); C. K. Shih, a whole series of compositionally homogeneous
fractions were prepared and disclosed. For example, the data in
TABLE I discloses polymer Sample B having a high degree of
homogeneity. Also, based on the reported data, the MWD of the
sample is very narrow. However, the polymers are not disclosed as
having intramolecular dispersity.
Representative prior art dealing with ethylene-alpha-olefin
copolymers as lubricating oil additives are as follows:
U.S. Pat. No. 3,697,429 to Engel et al discloses a blend of
ethylene-propylene copolymers having different ethylene contents,
i.e., a first copolymer of 40-83 wt. % ethylene and M.sub.w
/M.sub.n less than about 4.0 (preferably less than 2.6, e.g. 2.2)
and a second copolymer of 3-70 wt. % ethylene and M.sub.w /M.sub.n
less than 4.0, with the content of the first differing from the
second by at least 4 wt. % ethylene. These blends, when used as
V.I. improvers in lubricating oils, provide suitable low
temperature viscosity properties with minimal adverse interaction
between the oil pour depressant and the ethylene-propylene
copolymer.
U.S. Pat. No. 3,522,180 discloses copolymers of ethylene and
propylene having a number average molecular weight of 10,000 to
40,000 and a propylene content of 20 to 70 mole percent as V.I.
improvers in lube oils. The preferred M.sub.w /M.sub.n of these
copolymers is less than about 4.0.
U.S. Pat. No. 3,691,078 to Johnston et al discloses the use of
ethylene-propylene copolymers containing 25-55 wt. % ethylene which
have a pendent index of 18-33 and an average pendent size not
exceeding 10 carbon atoms as lube oil additives. The M.sub.w
/M.sub.n is less than about 8. These additives impart to the oil
good low temperature properties with respect to viscosity without
adversely affecting pour point depressants.
U.S. Pat. No. 3,551,336 to Jacobson et al discloses the use of
ethylene copolymers of 60-80 mole % ethylene, having no more than
1.3 wt. % of a polymer fraction which is insoluble in normal decane
at 55.degree. C. as an oil additive. Minimization of this
decane-insoluble fraction in the polymer reduces the tendency of
the polymer to form haze in the oil, which haze is evidence of low
temperature instability probably caused by adverse interaction with
pour depressant additives. The M.sub.w /M.sub.n of these copolymers
is "surprisingly narrow" and is less than about 4.0, preferably
less than 2.6, e.g., 2.2.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings depict, for illustration purposes only,
processes embodied by the present invention, wherein:
FIG. 9 is a schematic representation of a process for producing
polymer in accordance with the present invention,
FIG. 2 schematically illustrates how the process depicted in FIG. 1
can be integrated into a lube oil additive process,
FIG. 3 is a graphical illustration of a technique for determining
Intra-CD of a copolymer,
FIG. 4 graphically illustrates various copolymer structures that
can be attained using processes in accordance with the present
invention,
FIG. 5 is a graphic representation of polymer concentration vs.
residence time for consideration with Example 2 herein, and
FIG. 6 is a graphic representation of intramolecular compositional
dispersity (Intra-CD) of copolymer chains made with additional
monomer feeds downstream of the reactor inlet as in Example 3.
DETAILED DESCRIPTION OF THE INVENTION
As already noted above, the present invention is drawn to novel
copolymer of ethylene and at least one other alpha-olefin monomer
which copolymer is intramolecularly heterogeneous and
intermolecularly homogeneous and has an MWD characterized by at
least one of M.sub.w /M.sub.n of less than 2 and M.sub.z /M.sub.w
of less than 1.8. More specifically, copolymer in accordance with
the present invention comprises intramolecularly heterogeneous
chains wherein at least two portions of an individual
intramolecularly heterogeneous chain, each portion comprising at
least 5 weight percent of the chain, differ in composition from one
another by at least 5 weight percent ethylene, wherein the
intermolecular compositional dispersity of the polymer is such that
95 wt. % of the polymer chains have a composition 15% or less
different in ethylene from the average weight percent ethylene
composition, and wherein the copolymer is characterized by at least
one of a ratio of M.sub.w /M.sub.n of less than 2 and a ratio of
M.sub.z /M.sub.w of less than 1.8.
Since the present invention is considered to be most preferred in
the context of ethylene-propylene (EPM) or ethylene-propylene-diene
(EPDM) copolymers, it will be described in detail in the context of
EPM and/or EPDM.
Copolymer in accordance with the present invention is preferably
made in a tubular reactor. When produced in a tubular reactor with
monomer feed only at the tube inlet, it is known that at the
beginning of the tubular reactor ethylene, due to its high
reactivity, will be preferentially polymerized. However, the
concentration of monomers changes along the tube in favor of
propylene as the ethylene is depleted. The result is copolymer
chains which are higher in ethylene concentration in the chain
segments grown near the reactor inlet (as defined at the point at
which the polymerization reaction commences), and higher in
propylene concentration in the chain segments formed near the
reactor outlet. An illustrative copolymer chain of
ethylene-propylene is schematically presented below with E
representing ethylene constituents and P representing propylene
constituents in the chain: ##STR1##
As can be seen from this illustrative schematic chain, the far
left-hand segment (1) thereof represents that portion of the chain
formed at the reactor inlet where the reaction mixture is
proportionately richer in the more reactive constituent ethylene.
This segment comprises four ethylene molecules and one propylene
molecule. However, as subsequent segments are formed from left to
right with the more reactive ethylene being depleted and the
reaction mixture proportionately increasing in propylene
concentration, the subsequent chain segments become more
concentrated in propylene. The resulting chain is intramolecularly
heterogeneous.
In the event that more than two monomers are used, e.g., in the
production of EPDM using a diene termonomer, for purposes of
describing the present invention all properties related to
homogeneity and heterogeneity will refer to the relative ratio of
ethylene to the other monomers in the chain. The property, of the
copolymer discussed herein, related to intramolecular compositional
dispersity (compositional variation within a chain) shall be
referred to as Intra-CD, and that related to intermolecular
compositional dispersity (compositional variation between chains)
shall be referred to as Inter-CD.
For copolymers in accordance with the present invention,
composition can vary between chains as well as along the length of
the chain. An object of this invention is to minimize the amount of
interchain variation. The Inter-CD can be characterized by the
difference in composition between some fraction of the copolymer
and the average composition, as well as by the total difference in
composition between the copolymer fractions containing the highest
and lowest quantity of ethylene. Techniques for measuring the
breadth of the Inter-CD are known as illustrated by Junghanns et al
wherein a p-xylene-dimethylformamide solvent/non-solvent was used
to fractionate copolymer into fractions of differing intermolecular
composition. Other solvent/non-solvent systems can be used such as
hexane-2-propanol, as will be discussed in more detail below.
The Inter-CD of copolymer in accordance with the present invention
is such that 95 wt. % of the copolymer chains have an ethylene
composition that differs from the average weight percent ethylene
composition by 15 wt. % or less. The preferred Inter-CD is about
13% or less, with the most preferred being about 10% or less. In
comparison, Junghanns et al found that their tubular reactor
copolymer had an Inter-CD of greater than 15 weight %.
Broadly, the Intra-CD of copolymer in-accordance with the present
invention is such that at least two portions of an individual
intramolecularly heterogeneous chain, each portion comprising at
least 5 weight percent of the chain, differ in-composition from one
another by at least 5 weight percent ethylene. Unless otherwise
indicated, this property of Intra-CD as referred to herein is based
upon at least two 5 weight percent portions of copolymer chain. The
Intra-CD of copolymer in accordance with the present invention can
be such that at least two portions of copolymer chain differ by at
least 10 weight percent ethylene. Differences of at least 20 weight
percent, as well as, of at least 40 weight percent ethylene are
also considered to be in accordance with the present invention.
The experimental procedure for determining Intra-CD is as follows.
First the Inter-CD is established as described below, then the
polymer chain is broken into fragments along its contour and the
Inter-CD of the fragments is determined. The difference in the two
results is due to Intra-CD as can be seen in the illustrative
example below.
Consider a heterogeneous sample polymer containing 30 monomer
units. It consists of 3 molecules designated A, B, C.
______________________________________ A
EEEEPEEEPEEEPPEEPPEPPPEPPPPPPP B EEEEEPEEEPEEEPPEEEPPPEPPPEEPPP C
EEPEEEPEEEPEEEPEEEPPEEPPPEEPPP
______________________________________
Molecule A is 36.8 wt. % ethylene, B is 46.6%,.and C is 50%
ethylene. The average ethylene content for the mixture is 44.3%.
For this sample the Inter-CD is such that the highest ethylene
polymer contains 5.7% more ethylene than the average while the
lowest ethylene content polymer contains 7.5% less ethylene than
the average. Or, in other words, 100 weight % of the polymer is
within +5.7% and -7.5% ethylene about an average of 44.3%.
Accordingly, the Inter-CD is 7.5% when the given weight % of the
polymer is 100%. The distribution may be represented graphically as
by curve 1 in FIG. 3.
If the chains are broken into fragments, there will be new
Inter-CD. For simplicity, consider first breaking only molecule A
into fragments shown by the slashes as follows:
Portions of 72.7%, 72.7%, 50%, 30.8%, 14.3% and 0% ethylene are
obtained. If molecules B and C are similarly broken and the weight
fractions of similar composition are grouped the new Inter-CD shown
by curve 2 in FIG. 3 is obtained. The difference between the two
curves in the figure is due to Intra-CD.
Consideration of such data, especially near the end point ranges,
demonstrates that for this sample at least 5% of the chain contour
represented by the cumulative weight % range (a) differs in
composition from another section by at least 15% ethylene shown as
(b), the difference between the two curves. The difference in
composition represented by (b) cannot be intermolecular. If it
were, the separation process for the original polymer would have
revealed the higher ethylene contents seen only for the degraded
chain.
The compositional differences shown by (b) and (d) in the figure
between original and fragmented chains give minimum values for
Intra-CD. The Intra-CD must be at least that great, for chain
sections have been isolated which are the given difference in
composition (b) or (d) from the highest or lowest composition
polymer isolated from the original. We know in this example that
the original polymer represented at (b) had sections of 72.7%
ethylene and 0% ethylene in the same chain. It is highly likely
that due to the inefficiency of the fractionation process any real
polymer with Intra-CD examined will have sections of lower or
higher ethylene connected along its contour than that shown by the
end points of the fractionation of the original polymer. Thus, this
procedure determines a lower bound for Intra-CD. To enhance the
detection, the original whole polymer can be fractionated (e.g.,
separate molecule A from molecule B from molecule C in the
hypothetical example) with these fractions refractionated until
they show no (or less) Inter-CD. Subsequent fragmentation of this
intermolecularly homogeneous fraction now reveals the total
Intra-CD. In principle, for the example, if molecule A were
isolated, fragmented, fractionated and analyzed, the Intra-CD for
the chain sections would be 72.7-0%=72.7% rather than
72.7-50%=22.7% seen by fractionating the whole mixture of molecules
A, B, and C.
In order to determine the fraction of a polymer which is
intramolecularly heterogeneous in a mixture of polymers combined
from several sources the mixture must be separated into fractions
which show no further heterogenity upon subsequent fractionation.
These fractions are subsequently fractured and fractionated to
reveal which are heterogeneous.
The fragments into which the original polymer is broken should be
large enough to avoid end effects and to give a reasonable
opportunity for the normal statistical distribution of segments to
form over a given monomer conversion range in the polymerization.
Intervals of ca 5 weight % of the polymer are convenient. For
example, at an average polymer molecular weight of about 105,
fragments of ca 5000 molecular weight are appropriate. A detailed
mathematical analysis of plug flow or batch polymerization
indicates that the rate of change of composition along the polymer
chain contour will be most severe at high ethylene conversion near
the end of the polymerization. The shortest fragments are needed
here to show the low ethylene content sections.
The best available technique for determination of compositional
dispersity for non-polar polymers is solvent/non-solvent
fractionation which is based on the thermodynamics of phase
separation. This technique is described in "Polymer Fractionation",
M. Cantow editor, Academic 1967, p.341 ff and in H. Inagaki, T.
Tanaku, Developments in Polymer Characterization, 3, 1 (1982).
These are incorporated herein by reference.
For non-crystalline copolymers of ethylene and propylene, molecular
weight governs insolubility more than does composition in a
solvent/non-solvent solution. High molecular weight polymer is less
soluble in a given solvent mix. Also, there is a systematic
correlation of molecular weight with ethylene content for the
polymers described herein. Since ethylene polymerizes much more
rapidly than propylene, high ethylene polymer also tends to be high
in molecular weight. Additionally, chains rich in ethylene tend to
be less soluble in hydrocarbon/polar non-solvent mixtures than
propylene-rich chains. Thus the high molecular weight, high
ethylene chains are easily separated on the basis of
thermodynamics.
A fractionation procedure is as follows: Unfragmented polymer is
dissolved in n-hexane at 23.degree. C. to form ca a 1% solution (1
g polymer/100 cc hexane). Isopropyl alcohol is titrated into the
solution until turbidity appears at which time the precipitate is
allowed to settle. The supernatant liquid is removed and the
precipitate is dried by pressing between Mylar.RTM. (polyethylene
terphthalate) film at 150.degree. C. Ethylene content is determined
by ASTM method D-3900. Titration is resumed and subsequent
fractions are recovered and analyzed until 100% of the polymer is
collected. The titrations are ideally controlled to produce
fractions of 5-10% by weight of the original polymer especially at
the extremes of composition.
To demonstrate the breadth of the distribution, the data are
plotted as % ethylene versus the cumulative weight of polymer as
defined by the sum of half the weight % of the fraction of that
composition plus the total weight % of the previously collected
fractions.
Another portion of the original polymer is broken into fragments. A
suitable method for doing this is by thermal degradation according
to the following procedure: In a sealed container in a
nitrogen-purged oven, a 2 mm thick layer of the polymer is heated
for 60 minutes at 330.degree. C. This should be adequate to reduce
a 105 molecular weight polymer to fragments of ca 5000 molecular
weight. Such degradation does not change the average ethylene
content of the polymer. This polymer is fractionated by the same
procedure as the high molecular weight precursor. Ethylene content
is measured, as well as molecular weight on selected fractions.
Ethylene content is measured by ASTM-D3900 for
ethylene-propylene-copolymers between 35 and 85 wt. % ethylene.
Above 85% ASTM-D2238 can be used to obtain methyl group
concentrations which are related to percent ethylene in an
unambiguous manner for ethylene-propylene copolymers. When
comonomers other than propylene are employed no ASTM tests covering
a wide range of ethylene contents are available, however, proton
and carbon 13 nuclear magnetic resonance can be employed to
determine the composition of such polymers. These are absolute
techniques requiring no calibration when operated such that all
nucleii contribute equally to the spectra. For ranges not covered
by the ASTM tests for ethylene-propylene copolymers, these nuclear
magnetic resonance methods can also be used.
Molecular weight and molecular weight distribution are measured
using a Waters 150 gel permeation chromatograph equipped with a
Chromatix KMX-6 on-line light scattering photometer. The system is
used at 135.degree. C. with 1,2,4 trichlorobenzene as mobile phase.
Showdex (Showa-Denko America, Inc.) polystyrene gel columns 802,
803, 804 and 805 are used. This technique is discussed in "Liquid
Chromatography of Polymers and Related Materials III", J. Cazes
editor. Marcel Dekker, 1981, p. 207 (incorporated herein by
reference). No corrections for column spreading are employed;
however, data on generally accepted standards, e.g., National
Bureau of Standards Polyethene 1484 and anionically produced
hydrogenated polyisoprenes (an alternating ethylene-propylene
copolymer) demonstrate that such corrections on M.sub.w /M.sub.n or
M.sub.z /M.sub.w are less than 0.05 unit. M.sub.w /M.sub.n is
calculated from an elution time-molecular weight relationship
whereas M.sub.z /M.sub.w is evaluated using the light scattering
photometer. The numerical analyses can be performed using the
commercially available computer software GPC2, MOLWT 2 available
from LDC/Milton Roy-Riviera Beach, Fla.
As-already noted, copolymers in accordance with the present
invention are comprised of ethylene and at least one other
alpha-olefin. It is believed that such alpha-olefins could include
those containing 3 to 18 carbon atoms, e.g., propylene, butene-1,
pentene-1, etc. Alpha-olefins of 3 to 6 carbons are preferred due
to economic considerations. The most preferred copolymers in
accordance with the present invention are those comprised of
ethylene and propylene or ethylene, propylene and diene.
As is well known to those skilled in the art, copolymers of
ethylene and higher alpha-olefins such as propylene often include
other polymerizable monomers. Typical of these other monomers may
be non-conjugated dienes such as the following non-limiting
examples:
a. straight chain acyclic dienes such as: 1,4hexadiene;
1,6-octadiene;
b. branched chain acyclic dienes such as: 5-methyl-1, 4-hexadiene;
3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene and the
mixed isomers of dihydro-myrcene and dihydroocinene;
c. single ring alicyclic dienes such as: 1,4-cyclohexadiene;
1,5-cyclooctadiene; and 1,5-cyclododecadiene;
d. multi-ring alicyclic fused and bridged ring dienes such as:
tetrahydroindene; methyltetrahydroindene; dicyclopentadiene;
bicyclo-(2,2,1) -hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl
and cycloalkylidene norbornenes such as 5-methylene-2-norbornene
(MNB), 5-ethylidene-2-norbornene (ENB), 5-propyl-2-norbornene,
5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl) -2-norbornene;
5-cyclohexylidene-2-norbornene.
Of the non-conjugated dienes typically used to prepare these
copolymers, dienes containing at least one of the double bonds in a
strained ring are preferred. The most preferred diene is
5-ethylidene-2-norbornene (ENB). The amount of diene (wt. basis) in
the copolymer could be from about 0% to 20% with 0% to 15% being
preferred. The most preferred range is 0% to 10%.
As already noted, the most preferred copolymer in accordance with
the present invention is ethylene-propylene or
ethylene-propylene-diene. In either event, the average ethylene
content of the copolymer could be as low as about 10% on a weight
basis. The preferred minimum is about 25%. A more preferred minimum
is about 30%. The maximum ethylene content could be about 90% on a
weight basis. The preferred maximum is about 85%, with the most
preferred being about 80%.
The molecular weight of copolymer made in accordance with the
present invention can vary over a wide range. It is believed that
the weight average molecular weight could be as low as about 2,000.
The preferred minimum is about 10,000. The most preferred minimum
is about 20,000. It is believed that the maximum weight average
molecular weight could be as high as about 12,000,000. The
preferred maximum is about 1,000,000. The most preferred maximum is
about 750,000.
Another feature of copolymer made in accordance with the present
invention is that the molecular weight distribution (MWD) is very
narrow, as characterized by at least one of a ratio of M.sub.w
/M.sub.n of less than 2 and a ratio of M.sub.z /M.sub.w of less
than 1.8. As relates to EPM and EPDM, some typical advantages of
such copolymers having narrow MWD are greater resistance to shear
degradation, and when compounded and vulcanized, faster cure and
better physical properties than broader MWD materials. Particularly
for oil additive applications, the preferred copolymers have
M.sub.w /M.sub.n less than about 1.6, with less than about 1.4
being most preferred. The preferred M.sub.z /M.sub.w is less than
about 1.5, with less than about 1.3 being most preferred.
Processes in accordance with the present invention produce
copolymer by polymerization of a reaction mixture comprised of
catalyst, ethylene and at least one additional alpha-olefin
monomer. Solution polymerizations are preferred.
Any known solvent for the reaction mixture that is effective for
the purpose can be used in conducting solution polymerizations in
accordance with the present invention. For example, suitable
solvents would be hydrocarbon solvents such as aliphatic,
cycloaliphatic and aromatic hydrocarbon solvents, or halogenated
versions of such solvents. The preferred solvents are C.sub.12 or
lower, straight chain or branched chain, saturated hydrocarbons,
C.sub.5 to C.sub.9 saturated alicyclic or aromatic hydrocarbons or
C.sub.2 to C.sub.6 halogenated hydrocarbons. Most preferred are
C.sub.12 or lower, straight 11 chain or branched chain
hydrocarbons, particularly hexane. Nonlimiting illustrative
examples of solvents are butane, pentane, hexane, heptane,
cyclopentane, cyclohexane, cycloheptane, methyl cyclopentane,
methyl cyclohexane, isooctane, benzene, toluene, xylene,
chloroform, chlorobenzenes, tetrachloroethylene, dichloroethane and
trichloroethane.
These processes are carried out in a mix-free reactor system, which
is one in which substantially no mixing occurs between portions of
the reaction mixture that contain polymer chains initiated at
different times. Suitable reactors are a continuous flow tubular or
a stirred batch reactor. A tubular reactor is well known and is
designed to minimize mixing of the reactants in the direction of
flow. As a result, reactant concentration will vary along the
reactor length. In contrast, the reaction mixture in a continuous
flow stirred tank reactor (CFSTR) is blended with the incoming feed
to produce a solution of essentially uniform composition everywhere
in the reactor. Consequently, the growing chains in a portion of
the reaction mixture will have a variety of ages and thus a single
CFSTR is not suitable for the process of this invention. However,
it is well known that 3 or more stirred tanks in series with all of
the catalyst fed to the first reactor can approximate the
performance of a tubular reactor. Accordingly, such tanks in series
are considered to be in accordance with the present invention.
A batch reactor is a suitable vessel, preferably equipped with
adequate agitation, to which the catalyst, solvent, and monomer are
added at the start of the polymerization. The charge of reactants
is then left to polymerize for a time long enough to produce the
desired product. For economic reasons, a tubular reactor is
preferred to a batch reactor for carrying out the processes of this
invention.
In addition to the importance of the reactor system to make
copolymers in accordance with the present invention, the
polymerization should be conducted such that:
a. the catalyst system produces essentially one active catalyst
species,
b. the reaction mixture is essentially free of chain transfer
agents, and
c. the polymer-chains are essentially all initiated simultaneously,
which is at the same time for a batch reactor or at the same point
along the length of the tube for a tubular reactor.
The desired polymer can be obtained if additional solvent and
reactants (e.g., at least one of the ethylene, alpha-olefin and
diene) are added either along the length of a tubular reactor or
during the course of polymerization in a batch reactor. Operating
in this fashion may be desirable in certain circumstances to
control the polymerization rate or polymer composition. However, it
is necessary to add essentially all of the catalyst at the inlet of
the tube or at the onset of batch reactor operation to meet the
requirement that essentially all polymer chains are initiated
simultaneously.
Accordingly, processes in accordance with the present invention are
carried out:
(a) in at least one mix-free reactor,
(b) using a catalyst system that produces essentially one active
catalyst species,
(c) using at least one reaction mixture which is essentially
transfer agent-free, and
(d) in such a manner and under conditions sufficient to initiate
propagation of essentially all polymer chains simultaneously.
Since the tubular reactor is the preferred reactor system for
carrying out processes in accordance with the present invention,
the following illustrative descriptions and examples are drawn to
that system, but will apply to other reactor systems as will
readily occur to the artisan having the benefit of the present
disclosure.
In practicing processes in accordance with the present invention,
use is preferably made of at least one tubular reactor. Thus, in
its simplest form, such a process would make use of but a single
reactor. However, as would readily occur to the artisan having the
benefit of the present disclosure, more than one reactor could be
used, either in parallel for economic reasons, or in series with
multiple monomer feed to vary intramolecular composition.
For example, various structures can be prepared by adding
additional monomer(s) during the course of the polymerization, as
shown in FIG. 4, wherein composition is plotted versus position
along the contour length of the chain. The Intra-CD of curve 1 is
obtained by feeding all of the monomers at the tubular reactor
inlet or at the start of a batch reaction. In comparison, the
Intra-CD of curve 2 can be made by adding additional ethylene at a
point along the tube or, in a batch reactor, where the chains have
reached about half their length. The Intra-CD's of Curve 3 requires
multiple feed additions. The Intra-CD of curve 4 can be formed if
additional comonomer rather than ethylene is added. This structure
permits a whole ethylene composition range to be omitted from the
chain. In each case, a third or more comonomers may be added.
The composition of the catalyst used to produce alpha-olefin
copolymers has a profound effect on copolymer product properties
such as compositional dispersity and MWD. The catalyst utilized in
practicing processes in accordance with the present invention
should be such as to yield essentially one active catalyst species
in the reaction mixture. More specifically, it should yield one
primary active catalyst species which provides for substantially
all of the polymerization reaction. Additional active catalyst
species could be present, provided the copolymer product is in
accordance with the present invention, e.g., narrow MWD and
Inter-CD. It is believed that such additional active catalyst
species could provide as much as 35% (weight) of the total
copolymer. Preferably, they should account for about 10% or less cf
the copolymer. Thus, the essentially one active species should
provide for at least 65% of the total copolymer produced,
preferably for at least 90% thereof. The extent to which a catalyst
species contributes to the polymerization can be readily determined
using the below-described techniques for characterizing catalyst
according to the number of active catalyst species.
Techniques for characterizing catalyst according to the number of
active catalyst species are within the skill of the art, as
evidenced by an article entitled "Ethylene-Propylene Copolymers.
Reactivity Ratios, Evaluation and Significance", C. Cozewith and G.
Ver Strate, Macromolecules, 4, 482 (1971), which is incorporated
herein by reference.
It is disclosed by the authors that copolymers made in a continuous
flow stirred reactor should have an MWD characterized by M.sub.w
/M.sub.n =2 and a narrow Inter-CD when one active catalyst species
is present. By a combination of fractionation and gel permeation
chromatography (GPC) it is shown that for single active species
catalysts the compositions of the fractions vary no more than
.+-.3% about the average and the MWD (weight to number average
ratio) for these samples approaches two (2). It is this latter
characteristic (M.sub.w /M.sub.n of about 2) that is deemed the
more important in identifying a single active catalyst species. On
the other hand, other catalysts gave copolymer with an Inter-CD
greater than .+-.10% about the average and multi-modal MWD often
with M.sub.w /M.sub.n greater than 10. These other catalysts are
deemed to have more than one active species.
Catalyst systems to be used in carrying out processes in accordance
with the present invention may be Ziegler catalysts, which may
typically include:
(a) a compound of a transition metal, i.e., a metal of Groups I-B,
III-B, IVB, VB, VIB, VIIB and VIII of the Periodic Table, and (b)
an organometal compound of a metal of Groups I-A, II-A, II-B and
III-A of the Periodic Table.
The preferred catalyst system in practicing processes in accordance
with the present invention comprises hydrocarbon-soluble vanadium
compound in which the vanadium valence is 3 to 5 and
organo-aluminum compound, with the proviso that the catalyst system
yields essentially one active catalyst species as described above.
At least one of the vanadium compound/organo-aluminum pair selected
must also contain a valence-bonded halogen.
In terms of formulas, vanadium compounds useful in practicing
processes in accordance with the present invention could be:
##STR2## where n=2-3 and B=Lewis base capable of making
hydrocarbon-soluble complexes with VCl.sub.3, such as
tetrahydrofuran, 2-methyl-tetrahydrofuran and dimethyl
pyridine.
In formula 1 above, R preferably represents a C.sub.1 to C.sub.10
aliphatic, alicyclic or aromatic hydrocarbon radical such as ethyl
(Et), phenyl, isopropyl, butyl, propyl, n-butyl, i-butyl, t-butyl,
hexyl, cyclohexyl, octyl, naphthyl, etc. Non-limiting illustrative
examples of formula (1) and (2) compounds are vanadyl trihalides,
alkoxy halides and alkoxides such as VOCl.sub.3, VOCl.sub.2 (OBu)
where Bu=butyl, and VO(OC.sub.2 H.sub.5).sub.3. The most preferred
vanadium compounds are VCl.sub.4, VOCl.sub.3, and VOCl.sub.2
(OR).
As already noted, the co-catalyst is preferably organo-aluminum
compound. In terms of chemical formulas, these compounds could be
as follows:
______________________________________ AlR.sub.3, Al(OR')R.sub.2 Al
R.sub.2 Cl, R.sub.2 Al-O-AlR.sub.2 AlR'RCl AlR.sub.2 I A1.sub.2
R.sub.3 C13, and AlRC1.sub.2,
______________________________________
where R and R' represent hydrocarbon radicals, the same or
different, as described above with respect to the vanadium compound
formula. The most preferred organo-aluminum compound is an aluminum
alkyl sesquichloride such as Al.sub.2 Et.sub.3 Cl.sub.3 or Al.sub.2
(iBu).sub.3 Cl.sub.3.
In terms of performance, a catalyst system comprised of VCl.sub.4
and Al.sub.2 R.sub.3 Cl.sub.3, preferably where R is ethyl, has
been shown to be particularly effective. For best catalyst
performance, the molar amounts of catalyst components added to the
reaction mixture should provide a molar ratio of aluminum/vanadium
(Al/V) of at least about 2. The preferred minimum Al/V is about 4.
The maximum Al/V is based primarily on the considerations of
catalyst expense and the desire to minimize the amount of chain
transfer that may be caused by the organo-aluminum compound (as
explained in detail below). Since, as is known certain
organo-aluminum compounds act as chain transfer agents, if too much
is present in the reaction mixture the M.sub.w /M.sub.n of the
copolymer may rise above 2. Based on these considerations, the
maximum Al/V could be about 25, however, a maximum of about 17 is
more preferred. The most preferred maximum is about.15.
Chain transfer agents for the Ziegler-catalyzed polymerization of
alpha-olefins are well known and are illustrated, by way of
example, by hydrogen or diethyl zinc for the production of EPM and
EPDM. Such agents are very commonly used to control the molecular
weight of EPM and EPDM produced in continuous flow stirred
reactors. For the essentially single active species Ziegler
catalyst systems used in accordance with the present invention,
addition of chain transfer agents to a CFSTR reduces the polymer
molecular weight but does not affect the molecular weight
distribution. On the other hand, chain transfer reactions during
tubular reactor polymerization in accordance with the present
invention broaden polymer molecular weight distribution and
Inter-CD. Thus the presence of chain transfer agents in the
reaction mixture should be minimized or omitted altogether.
Although difficult to generalize for all possible reactions, the
amount of chain transfer agent used should be limited to those
amounts that provide copolymer product in accordance with the
desired limits as regards MWD and compositional dispersity. It is
believed that the maximum amount of chain transfer agent present in
the reaction mixture could be as high as about 0.2 mol/mol of
transition metal, e.g., vanadium, again provided that the resulting
copolymer product is in accordance with the desired limits as
regards MWD and compositional dispersity. Even in the absence of
added chain transfer agent, chain transfer reactions can occur
because propylene and the organo-aluminum cocatalyst can also act
as chain transfer agents. In general, among the organo-aluminum
compounds that in combination with the vanadium compound yield just
one active species, the organo-aluminum compound that gives the
highest copolymer molecular weight at acceptable catalyst activity
should be chosen. Furthermore, if the Al/V ratio has an effect on
the molecular weight of copolymer product, that Al/V should be used
which gives the highest molecular weight also at acceptable
catalyst activity. Chain transfer with propylene can best be
limited by avoiding excessive temperature during the polymerization
as described below.
Molecular weight distribution and Inter-CD are also broadened by
catalyst deactivation during the course of the polymerization which
leads to termination of growing chains. It is well known that the
vanadium-based Ziegler catalysts used in accordance with the
present invention are subject to such deactivation reactions which
depend to an extent upon the composition of the catalyst. Although
the relationship between active catalyst lifetime and catalyst
system composition is not known at present, for any given catalyst,
deactivation can be reduced by using the shortest residence time
and lowest temperature in the reactor that will produce the desired
monomer conversions.
Polymerizations in accordance with the present invention should be
conducted in such a manner and under conditions sufficient to
initiate propagation of essentially all copolymer chains
simultaneously. This can be accomplished by utilizing the process
steps and conditions described below.
The catalyst components are preferably premixed, that is, reacted
to form active catalyst outside of the reactor, to ensure rapid
chain initiation. Aging of the premixed catalyst system, that is,
the time spent by the catalyst components (e.g., vanadium compound
and organo-aluminum) in each other's presence outside of the
reactor, should preferably be kept within limits. If not aged for a
sufficient period of time, the components will not have reacted
with each other sufficiently to yield an adequate quantity of
active catalyst species, with the result of nonsimultaneous chain
initiation. Also, it is known that the activity of the catalyst
species will decrease with time so that the aging must be kept
below a maximum limit. It is believed that the minimum aging
period, depending on such factors as concentration of catalyst
components, temperature and mixing equipment, could be as low as
about 0.1 second. The preferred minimum aging period is about 0.5
second, while the most preferred minimum aging period is about 1
second. While the maximum aging period could be higher, for the
preferred vanadium/organo-aluminum catalyst system the preferred
maximum is about 200 seconds. A more preferred maximum is about 100
seconds. The most preferred maximum aging period is about 50
seconds. The premixing could be performed at low temperature such
as 40.degree. C. or below. It is preferred that the premixing be
performed at 25.degree. C. or below, with 15.degree. C. or below
being most preferred.
The temperature of the reaction mixture should also be kept within
certain limits. The temperature at the reactor inlet should be high
enough to provide complete, rapid chain initiation at the start of
the polymerization reaction. The length of time the reaction
mixture spends at high temperature must be short enough to minimize
the amount of undesirable chain transfer and catalyst deactivation
reactions.
Temperature control of the reaction mixture is complicated somewhat
by the fact that the polymerization reaction generates large
quantities of heat. This problem is, preferably, taken care of by
using prechilled feed to the reactor to absorb the heat of
polymerization. With this technique, the reactor is operated
adiabatically and the temperature is allowed to increase during the
course of polymerization. As an alternative to feed prechill, heat
can be removed from the reaction mixture, for example, by a heat
exchanger surrounding at least a portion of the reactor or by
well-known autorefrigeration techniques in the case of batch
reactors or multiple stirred reactors in series.
If adiabatic reactor operation is used, the inlet temperature of
the reactor feed could be about from -50.degree. C. to 150.degree.
C. It is believed that the outlet temperature of the reaction
mixture could be as high as about 200.degree. C. The preferred
maximum outlet temperature is about 70.degree. C. The most
preferred maximum is about 50.degree. C. In the absence of reactor
cooling, such as by a cooling jacket, to remove the heat of
polymerization, it has been determined that the temperature of the
reaction mixture will increase from reactor inlet to outlet by
about 13.degree. C. per weight percent of copolymer in the reaction
mixture (weight of copolymer per weight of solvent).
Having the benefit of the above disclosure, it would be well within
the skill of the art to determine the operating temperature
conditions for making copolymer in accordance with the present
invention. For example, assume an adiabatic reactor and an outlet
temperature of 35.degree. C. are desired for a reaction mixture
containing 5% copolymer. The reaction mixture will increase in
temperature by about 13.degree. C. for each weight percent
copolymer or 5 weight percent.times.13.degree. C./wt. %=65.degree.
C. To maintain an outlet temperature of 35.degree. C., it will thus
require a feed that has been prechilled to 35.degree. C.-65.degree.
C.=-30.degree. C. In the instance that external cooling is used to
absorb the heat of polymerization, the feed inlet temperature could
be higher with the other temperature constraints described above
otherwise being applicable.
Because of heat removal and reactor temperature limitations, the
preferred maximum copolymer concentration at the reactor outlet is
25 wt./100 wt. diluent. The most preferred maximum concentration is
15 wt/100 wt. There is no lower limit to concentration due to
reactor operability, but for economic reasons it is preferred to
have a copolymer concentration of at least 2 wt/100 wt. Most
preferred is a concentration of at least 3 wt/100 wt.
The rate of flow of the reaction mixture through the reactor should
be high enough to provide good mixing of the reactants in the
radial direction and minimize mixing in the axial direction. Good
radial mixing is beneficial not only to both the Intra-and Inter-CD
of the copolymer chains but also to minimize radial temperature
gradients due to the heat generated by the polymerization reaction.
Radial temperature gradients will tend to broaden the molecular
weight distribution of the copolymer since the polymerization rate
is faster in the high temperature regions resulting from poor heat
dissipation. The artisan will recognize that achievement of these
objectives is difficult in the case of highly viscous solutions.
This problem can be overcome to some extent through the use of
radial mixing devices such as static mixers (e.g., those produced
by the Kenics Corporation).
It is believed that residence time of the reaction mixture in the
mix-free reactor can vary over a wide range. It is believed that
the minimum could be as low as about 1 second. A preferred minimum
is about 10 seconds. The most preferred minimum is about 15
seconds. It is believed that the maximum could be as high as about
3600 seconds. A preferred maximum is about 1800 seconds. The most
preferred maximum is about 900 seconds.
With reference to the accompanying drawings, particularly FIG. 1,
reference numeral 1 generally refers to a premixing device for
premixing the catalyst components. For purposes of illustration, it
is assumed that a copolymer of ethylene and propylene (EPM) is to
be produced using as catalyst components vanadium tetrachloride and
ethyl aluminum sesqui chloride. The polymerization is an adiabatic,
solution polymerization process using hexane solvent for both the
catalyst system and the reaction mixture.
The premixing device 1 comprises a temperature control bath 2, a
fluid flow conduit 3 and mixing device 4 (e.g., a mixing tee). To
mixing device 4 are fed hexane solvent, vanadium tetrachloride and
ethyl aluminum sesqui chloride through feed conduits 5, 6 and 7,
respectively. Upon being mixed in mixing device 4, the resulting
catalyst mixture is caused to flow within conduit 3, optionally in
the form of a coiled tube, for a time long enough to produce the
active catalyst species at the temperature set by the temperature
bath. The temperature of the bath is set to give the desired
catalyst solution temperature in conduit 3 at the outlet of the
bath.
Upon leaving the premixing device, the catalyst solution flows
through conduit 8 into mixing zone 9 to provide an intimate mixing
with hexane solvent and reactants (ethylene and propylene) which
are fed through conduit 10. Any suitable mixing device can be used,
such as mechanical mixer, orifice mixer or mixing tee. For economic
reasons, the mixing tee is preferred. The residence time of the
reaction mixture in mixing zone 9 is kept short enough to prevent
significant polymer formation therein before being fed through
conduit 11 to tubular reactor 12. Alternatively, streams 8 and 10
can be fed directly to the inlet of reactor 12 if the flow rates
are high enough to accomplish the desired level of intimate mixing.
The hexane with dissolved monomers may be cooled upstream of mixing
zone 9 to provide the desired feed temperature at the reactor
inlet.
Tubular reactor 12 is shown with optional, intermediate feed points
13-15 where additional monomers (e.g., ethylene as shown) and/or
hexane can be fed to the reactor. The optional feeds would be used
in the instance where it would be desirable to control the
Intra-CD. While the reactor can be operated adiabatically, if
desired or necessary to maintain reaction mixture temperature
within desired limits, external cooling means such as a cooling
jacket surrounding at least a portion of the reactor system 12 can
be provided.
With reference to FIG. 2 which schematically illustrates a process
for mixing copolymer with lube oil, copolymer product from reactor
12 is fed through conduit 16 to deashing section 17 wherein
catalyst residues are removed from the reaction mixture in a known
manner (known as deashing). The vanadium and aluminum compound
residues are removed by reacting them with water to form
hydrocarbon-insoluble hydroxides and then extracting the hydroxides
into dilute acid.
After separating the aqueous and hydrocarbon phases, for instance
in a gravity settler, the polymer solution, which primarily
contains solvent, unreacted monomers and copolymer product (EPM) is
fed through conduit 18 to lube oil mixing tank 19. Of course, tank
19 could be a staged series of tanks. Hot lube oil is fed through
conduit 20 to mixing tank 19, wherein the remaining reaction
mixture is heated up such that the remaining hexane and unreacted
monomers are vaporized and removed through recycle conduit 21
through which they flow back for reuse in premixing device 1
following suitable purification to remove any catalyst poisons. The
copolymer product, being hydrocarbon-soluble, is now present in the
lube oil and is removed from tank 19 as a copolymer-in-oil
solution.
Alternatively, the copolymer solution from the gravity settler can
be steam distilled with subsequent extrusion drying of the polymer
and then mixed with a hydrocarbon mineral oil diluent to produce an
oil additive concentrate or lube oil additive.
Having thus described the above illustrative reactor system, it
will readily occur to the artisan that many variations can be made
within the scope of the present invention. For example, the
placement and number of multiple feed sites, the choice of
temperature profile during polymerization and the concentrations of
reactants can be varied to suit the end-use application.
By practicing processes in accordance with the present invention,
alpha-olefin copolymers having very narrow MWD can be made by
direct polymerization. Although narrow MWD copolymers can be made
using other known techniques, such as by fractionation or
mechanical degradation, these techniques are considered to be
impractical to the extent of being unsuitable for commercial-scale
operation. As regards EPDM made in accordance with the present
invention, the products have enhanced cure properties at a given
Mooney Viscosity. As regards EPM, the products have good shear
stability and excellent low temperature properties which make them
especially suitable for lube oil applications. For lube oil
applications, the narrower the MWD of the polymer, the better the
copolymer is considered to be.
A lubricating oil composition in accordance with the present
invention comprises a major amount of basestock lubricating oil
(lube oil) of lubricating viscosity which contains an effective
amount of viscosity index improver being a copolymer of ethylene
and at least one other alphaolefin as described in detail above.
More specifically, the copolymer should have a MWD characterized by
at least one of a ratio of M.sub.w /M.sub.n of less than 2 and a
ratio of M.sub.z /M.sub.w of less than 1.8. The preferred ratio of
is less than about 1.6, with less than about 1.4 being preferred.
The preferred M.sub.z /M.sub.w is less than about 1.5, with less
than about 1.3 being most preferred.
It is preferred that the Intra-CD of the copolymer is such that at
least two portions of an individual intramolecularly heterogeneous
chain, each portion comprising at least 5 weight percent of said
chain, differ in composition from one another by at least 5 weight
percent ethylene. The Intra-CD can be such that at least two
portions of copolymer chain differ by at least 10 weight percent
ethylene. Differences of at least 20 weight percent, as well as, 40
weight percent ethylene are also considered to be in accordance
with the present invention.
It is also preferred that the Inter-CD of the copolymer is such
that 95 wt. % of the copolymer chains have an ethylene composition
that differs from the copolymer average weight percent ethylene
composition by 15 wt. % or less. The preferred Inter-CD is about
13% or less, with the most preferred being about 10% or less.
In a most preferred embodiment, the copolymer has all of the MWD,
Intra-CD and Inter-CD characteristics described above when
incorporated in a lubricating oil or oil additive concentrate
composition. In current practice, ethylene-propylene copolymer is
most preferred. The preferred ethylene content of the copolymer, on
a weight basis, for use as a lube oil additive is about from 30% to
75%.
For lube oil additive applications, it is believed that the
copolymer could have a weight average molecular weight as low as
about 5,000. The preferred minimum is about 15,000, with about
50,000 being the most preferred minimum. <It is believed that
the maximum weight average molecular weight could be as high as
about 500,000. The preferred maximum is about 300,000, with about
250,000 being the most preferred maximum.
Copolymers of this invention may be employed in lubricating oils as
viscosity index improvers cr viscosity modifiers in amounts varying
broadly from about 0.001 to 49 wt. % . The proportions giving the
best results will vary somewhat according to the nature of the
lubricating oil basestock and the specific purpose for which the
lubricant is to serve in a given case. When used as lubricating
oils for diesel or gasoline engine crankcase lubricants, the
polymer concentrations are within the range of about 0.1 to 15.0 wt
% of the total composition which are amounts effective to provide
viscosity index improvements. Typically such polymeric additives
are sold as oil additive concentrates wherein the additive is
present in amounts of about 5 to 50 wt %, preferably 6 to 25 wt %
based on the total amount of hydrocarbon mineral oil diluent for
the additive. The polymers of this invention are typically used in
lubricating oils based on a hydrocarbon mineral oil having a
viscosity of about 2-40 centistokes (ASTM D-445) at 99.degree. C.,
but lubricating oil basestocks comprised of a mixture of a
hydrocarbon mineral oil and up to about 25 wt % of a synthetic
lubricating oil such as esters of dibasic acids and complex esters
derived from monobasic acids, polyglycols, dibasic acids and
alcohols are also considered suitable.
Finished lubricating oils containing the ethylene-alpha-olefin
polymers of the present invention will typically contain a number
of other conventional additives in amounts required to provide
their normal attendant functions and these include ashless
dispersants, metal or over-based metal detergent additives, zinc
dihydrocarbyl dithiophosphate, anti-wear additives, anti-oxidants,
pour depressants, rust inhibitors, fuel economy or friction
reducing additives and the like.
The ashless dispersants include the polyalkenyl or borated
polyalkenyl succinimide where the alkenyl group is derived from a
C.sub.3 -C.sub.4 olefin, especially polyisobutenyl having a number
average molecular weight of about 700 to 5,000. Other well known
dispersants include the oil soluble polyol esters of hydrocarbon
substituted succinic anhydride, e.g., polyisobutenyl succinic
anhydride and the oil soluble oxazoline and lactone oxazoline
dispersants derived from hydrocarbon substituted succinic anhydride
and di-substituted amino alcohols. Lubricating oils typically
contain about 0.5 to 5 wt. % of ashless dispersant.
The metal detergent additives suitable in the oil are known in the
art and include one or more members selected from the group
consisting of overbased oil-soluble calcium, magnesium and barium
phenates, sulfurized phenates, and sulfonates especially the
sulfonates of C.sub.16 -C.sub.50 alkyl substituted benzene or
toluene sulfonic acids which have a total base number of about 80
to 300. These overbased materials may be used as the sole metal
detergent additive or in combination with the same additives in the
neutral form but the overall metal detergent additive combination
should have a basicity as represented by the foregoing total base
number. Preferably they are present in amounts of from about 0.5 to
8 wt. % with a mixture of overbased magnesium sulfurized phenate
and neutral calcium sulfurized phenate, obtained from C.sub.8 to
C.sub.12 alkyl phenols being especially useful.
The anti-wear additives useful are the oil-soluble zinc
dihydrocarbyldithiophosphate having a total of at least 5 carbon
atoms, preferably alkyl groups of C.sub.4 -C.sub.8, typically used
in amounts of about 0.5-6% by weight.
Other suitable conventional viscosity index improvers, or viscosity
modifiers, are the olefin polymers such as other ethylene-propylene
copolymers (e.g., those disclosed in the prior art as discussed
above), polybutene, hydrogenated polymers and copolymers and
terpolymers of styrene with isoprene and/or butadiene, polymers of
alkyl acrylates or alkyl methacrylates, copolymers of alkyl
methacrylates with N-vinyl pyrollidone or dimethylaminoalkyl
methacrylate, post-grafted polymers of ethylenepropylene with an
active monomer such as maleic anhydride which may be further
reacted with alcohol or an alkylene polyamine, styrene-maleic
anhydride polymers post-reacted with alcohols and amines and the
like. These are used as required to provide the viscosity range
desired in the finished oil, in accordance with known formulating
techniques.
Examples of suitable oxidation inhibitors are hindered phenols,
such as 2,6-ditertiary-butyl-paracresol, amines, sulfurized phenols
and alkyl phenothiazines; usually a lubricating oil will contain
about 0.01 to 3 weight percent of oxidation inhibitor depending on
its effectiveness.
Rust inhibitors are employed in very small proportions such as
about 0.1 to 1 weight percent with suitable rust inhibitors being
exemplified by C.sub.9 -C.sub.30 aliphatic succinic acids or
anhydrides such as dodecenyl succinic anhydride.
Antifoam agents are typically the polysiloxane silicone polymers
present in amounts of about 0.01 to 1 weight percent.
Pour point depressants are used generally in amounts of from about
0.01 to about 10.0 wt. %, more typically from about 0.01 to about 1
wt. %, for most mineral oil basestocks of lubricating viscosity.
Illustrative of pour point depressants which are normally used in
lubricating oil compositions are polymers and copolymers of n-alkyl
methacrylate and n-alkyl acrylates, copolymers of di-n-alkyl
fumarate and vinyl acetate, alpha-olefin copolymers, alkylated
naphthalenes, copolymers or terpolymers of alpha-olefins and
styrene and/or alkyl styrene, styrene dialkyl maleic copolymers and
the like.
As noted above, copolymer products made in accordance with the
present invention have excellent low temperature properties which
makes them suitable for lube oil applications. Accordingly, lube
oil compositions made in accordance with the present invention
preferably have a Mini Rotary Viscosity (MRV) measurement in
centipoises (cps) at -25.degree. C. according to ASTM-D 3829 of
less than 30,000. A more preferred MRV is less than 20,000, with
less than 10,000 being most preferred.
With reference again to processes for making copolymer in
accordance with the present invention, it is well known that
certain combinations of vanadium and aluminum compounds that can
comprise the catalyst system can cause branching and gelation
during the polymerization for polymers containing high levels of
diene. To prevent this from happening Lewis bases such as ammonia,
tetrahydrofuran, pyridine, tributylamine, tetrahydrothiophene,
etc., can be added to the polymerization system using techniques
well known to those skilled in the art.
EXAMPLE 1
In this example, an ethylene-propylene copolymer was prepared in a
conventional continuous flow stirred tank reactor. Catalyst,
monomers and solvent were fed to a 3 gallon reactor at rates shown
in the accompanying Table I. Hexane was purified prior to use by
passing over 4A molecular sieves (Union Carbide, Linde Div. 4A
1/16" pellets) and silica gel (W. R. Grace Co., Davison Chemical
Div., PA-400 20-40 mesh) to remove polar impurities which act as
catalyst poisons. Gaseous ethylene and propylene were passed over
hot (270.degree. C.) CuO (Harshaw Chemical Co., CU1900 1/4"
spheres) to remove oxygen followed by mol sieve treatment for water
removal and then were combined with the hexane upstream of the
reactor and passed through a chiller which provided a low enough
temperature to completely dissolve the monomers in the hexane.
Polymerization temperature was controlled by allowing the cold feed
to absorb the heat of reaction generated by the polymerization. The
reactor outlet pressure was controlled at 413 kPa to ensure
dissolution of the monomers and a liquid filled reactor. 0 Catalyst
solution was prepared by dissolving 37.4 g of VCl.sub.4 in 7 l of
purified n-hexane. Cocatalyst consisted of 96.0 g Al.sub.2 Et.sub.3
Cl.sub.3 in 7 l of n-hexane. These solutions were fed to the
reactor at rates shown in Table I. For the case of catalyst
premixing the two solutions were premixed at 0.degree. C. for 10
seconds prior to entry into the reactor.
Copolymer was deashed by contacting with aqueous base and recovered
by steam distillation of the diluent with mill drying of the
product to remove residual volatiles. The product so prepared was
analyzed for composition, compositional distribution and molecular
weight distribution using the techniques discussed in the
specification. Results were as in Table I.
The copolymers were essentially compositionally homogeneous with
heterogeneity .+-.3% about the average, i.e. within experimental
error.
These results indicate that for copolymer made in a continuous flow
stirred reactor the M.sub.w /M.sub.n was about 2 and the Intra-CD
was less than 5% ethylene. Catalyst premixing had no effect on
M.sub.w /M.sub.n or compositional distribution. Experiments over a
range of polymerization conditions with the same catalyst system
produced polymers of similar structure.
TABLE I
__________________________________________________________________________
Example 1A Example 1B
__________________________________________________________________________
Reactor Inlet Temperature (.degree.C.) -40 -35 Reactor Temperature
(.degree.C.) 38 37.5 Reactor Feed Rates Hexane (kg/hr) 39.0 23.7
Ethylene (g/hr) 1037 775 Propylene (g/hr) 1404 1185 VCl.sub.4
(g/hr) 5.41 2.56 Al.sub.2 Et.sub.3 Cl.sub.3 (g/hr) 17.4 13.2
Catalyst Premixing Temperature (.degree.C.) Not premixed 0 Catalyst
Premixing Time (sec) Not premixed 10 Reactor Residence Time (min)
10.5 17.1 Rate of Polymerization (g/hr) 2256 1516 Catalyst
Efficiency (g polymer/g V) 416 591 (--Mw).sup.(a) 1.5 .times.
10.sup.5 2.1 .times. 10.sup.5 (--Mw/--Mn).sup.(b) 2.1 1.9
(--M.sub.z /--M.sub.w).sup.(a) 1.7 1.7 Average Composition
(Ethylene wt. %).sup.(c) 43 47
__________________________________________________________________________
Compositional Distribution.sup.(d) Intra-CD Original Fragmented
Inter- High Low max min max min CD Ethylene Ethylene
__________________________________________________________________________
Example 1A 48 42 48 45 +5 0 0 -1 Example 1B 48 42 50 46 +1 +2 0 -5
__________________________________________________________________________
.sup.(a) Determined by GPC/LALLS using total scattered light
intensity in 1,2,4 trichlorobenzene at 135.degree. C., Chromatix
KMX6, specific refractive index increment dn/dc = -.104
(g/cc).sup.-1 (see specification .sup.(b) Determined from an
elution timemolecular weight relationship as discussed in the
specification, data precision .+-..15 .sup.(c) Determined by ASTM
D3900 Method A. Data good to .+-.2% ethylene. .sup.(d) Composition
determined on fractions which comprise 5-20% of the original
polymer weight, hexaneisopropyl alcohol is solventnon solvent pair.
.sup.(e) InterCD is determined as the difference for 95 wt. % of
the polymer between the maximum and minimum of the original polymer
and the average composition .sup.(f) Chains fragmented to ca. 5% of
their original molecular weight. IntraCD is determined as the
difference in composition between the highes ethylene fractions of
the original and fragmented chains and between the lowest such
fractions.
EXAMPLE 2
This example is seen to illustrate the importance of reaction
conditions in practicing methods in accordance with the invention
such as catalyst premixing for making narrow MWD polymer with the
desired Intra-CD. In examples 2(B.) and 2(C.) the catalyst
components were premixed in order to obtain rapid chain initiation.
In example 2(A.) the polymerization conditions were similar, but
the catalyst components were fed separately to the reactor
inlet.
The polymerization reactor was a one-inch diameter pipe equipped
with Kenics static mixer elements along its length. Monomers,
hexane, catalyst, and cocatalyst were continuously fed to the
reactor at one end and the copolymer solution and unreacted
monomers were withdrawn from the other end. Monomers were purified
and reactor temperature and pressure was controlled as in Example
1.
A catalyst solution was prepared by dissolving 18.5 g of vanadium
tetrachloride, VCl.sub.4, in 5.0 l of purified n-hexane The
cocatalyst consisted of 142 g of ethyl aluminum sesqui chloride,
Al.sub.2 Et.sub.3 Cl.sub.3, in 5.0 l of purified n-hexane. In the
case of catalyst premixing, the two solutions were premixed at a
given temperature (as indicated in TABLE II) for 10 seconds prior
to entry into the reactor.
Table II lists the feed rates for the monomers, catalyst, and the
residence time of examples 2(A.), (B.), and (C.). Polymer was
recovered and analyzed as in Example 1.
FIG. 5 illustrates the polymer concentration-residence time
relationship, with concentration being presented in terms of
polymer concentration at residence time t (C.sub.At residence time
t)/polymer concentration at final t (C.sub.Final t) which exists at
the end of the reactor. It is evident that in example 2(B.) the
maximum polymerization rate occurs at about zero reaction time
indicating fast initiation of all the polymer chains. As a result,
a very narrow MWD EPM with (M.sub.w /M.sub.n) equal to 1.3 and
(M.sub.z /M.sub.w) of 1.2 was produced through a process in
accordance with the present invention. On the other hand, example
2(A.) shows that EPM with M.sub.w /M.sub.n greater than 2.0 and
M.sub.z /M.sub.w of 2.0 was obtained when the proper conditions
were not used. In this example, lack of premixing of the catalyst
components led to a reduced rate of chain initiation and broadened
MWD.
Samples of product were fractionated according to the procedure of
Example 1 and as disclosed in the specification Data appear in
Table II.
Sample A, made without catalyst premixing, had a broad Inter-CD
typical of the prior art (e.g., Junghanns). For samples B and C
Inter-CD was much reduced as a result cf the premixing.
Intra-CD is shown as the difference between the fractionation data
on the fragmented and unfragmented samples. For sample B, the
chains are shown to contain segments of at least 6% ethylene higher
than that isolatable on the unfragmented material. The residual
Inter-CD obscures the analysis of Intra-CD. To make the analysis
clearer, sample C was first fractionated and then one fraction (the
3rd) was refractionated showing it to be homogeneous with regard to
Inter-CD. Upon fragmentation a compositional dispersity as large as
the original whole polymer Inter-CD was obtained. Thus, those
chains must have had an Intra-CD of greater than 18%. The 2nd and
3rd fractions, which were similar, comprised more than 70% of the
original polymer showing that the Inter-CD which obscured the
Intra-CD was only due to a minor portion of the whole polymer.
Since the fractionation procedure might depend on the solvent
non-solvent pair used, a second combination, carbon
tetrachloride-ethyl acetate was used on the sample C whole polymer.
This pair was also used in the prior art. It is apparent from the
data of Table II that hexane-isopropanol separated the polymer more
efficiently than CCl.sub.4 -ethyl acetate.
TABLE II
__________________________________________________________________________
Example 2A Example 2B Example 2C
__________________________________________________________________________
Reactor Inlet Temperature (.degree.C.) -20 -10 -10 Reactor Outlet
Temperature (.degree.C.) -3 0 0 Reactor Feed Rates Hexane (kg/hr)
60.3 60.3 60.3 Ethylene (kg/hr) 0.4 0.22 0.22 Propylene (kg/hr) 3.2
2.0 2.0 VCl.sub.4 (g/hr) 2.22 2.22 2.22 Al.sub.2 Et.sub.3 Cl.sub.3
(g/hr) 20.5 17.0 71.0 Catalyst Premixing Temperature (.degree.C.)
-- 0 +10 Catalyst Premixing Time (sec) 0 10 10 Reactor Residence
Time (sec) 52 50 35 Rate of Polymerization (g/hr) 874 503 426
Catalyst Efficiency (g polymer/g VCl.sub.4) 394 227 192
(--Mw).sup.(a) 2.1 .times. 10.sup.5 1.4 .times. 10.sup.5 9.5
.times. 10.sup.4 (--M.sub.z /--M.sub.w).sup.(a) 2.0 1.2 1.2
(--Mw/--Mn).sup.(b) 2.70 1.3 1.2 Composition (ethene wt. %).sup.(c)
42.4 39.1 41.4
__________________________________________________________________________
Compositional Distribution.sup.(d) Original Fragmented Intra
CD.sup.(g) max min max min Inter CD.sup.(f) max min
__________________________________________________________________________
2A 55 25 -- -- +13 --.sup.(e) --.sup.(e) -17 2B 45 32 51 32 +6 +6 0
-7 2C 49 34 51 (39) +8 +2 --.sup.(e) -7 2C 3rd cut refractionated
42 39 48 32 6 -7 2C CCl.sub.4 -ethyl acetate 45 34 -- -- -- -- --
__________________________________________________________________________
.sup.(a) Determined by GPC/LALLS using total scattered light
intensity in 1,2,4 trichlorobenzene at 135.degree. C., Chromatix
KMX6, specific refractive index increment dn/dc =
-.104(g/cc).sup.-1 (see specification) .sup.(b) Determined from an
elution timemolecular weight relationship as discussed in the
specification data precision .+-..15 .sup.(c) Determined by ASTM
D3900 Method A. Data good to .+-.2% ethylene. .sup.(d) Composition
determined on fractions which comprise 5-20% of the original
polymer weight, hexame isopropyl alcohol is solventnon solvent
pair. .sup.(e) In these cases inter CD obscured intra CD so no
increase in CD was shown on fragmentation. .sup.(f) InterCD is
determined as the difference for 95 wt. % of the polymer between
the maximum and minimum of the original polymer and the average
composition. .sup.(g) Chains fragmented to ca. 5% of their original
molecular weight. IntraCD is determined as the difference in
composition between the highes ethylene fractions of the original
and fragmented chains and between the lowest such fractions.
EXAMPLE 3
This example illustrates the use of additional monomer feed
downstream of the reactor inlet (multiple feed points) to vary
polymer composition and compositional distribution while
maintaining a narrow MWD. In example 3(B.), a second hexane stream
containing only ethylene was fed into the reactor downstream of the
inlet in addition to those feeds used at the inlet. In example
3(A.), the polymerization conditions were the same except there was
no second ethylene feed. The polymerization procedures of example
2(B.) were repeated. The process conditions are listed in Table
III.
The data listed in Table III show that the sample made with an
additional monomer feed downstream of the reactor inlet had the
same MWD as the one made with all the monomer feed at the reactor
inlet. This combined with the increases in ethylene composition of
the "2nd feed point" sample and the molecular weight of the final
sample in example 3(B.) indicate that the monomers in the second
feed had been added to the growing polymer chains. Therefore, the
Intra-CD of the final product must be as shown schematically in
FIG. 6.
It is apparent that since the chains continue to grow down the tube
that a variety of structures can be produced by using multiple feed
points as noted in the specification.
TABLE III ______________________________________ Example Example 3B
3A ______________________________________ Solvent Temperature
(.degree.C.) Main Feed -10 -10 Second Feed 0 -- Reactor Outlet
Temperature (.degree.C.) +3 0 Reactor Feed Rates Hexane (kg/hr)
Main Feed 60.7 60.7 Second Feed 9.9 -- Ethylene (kg/hr) Main Feed
0.22 0.22 Second Feed 0.10 -- Propylene (kg/hr) 2.0 2.0 VCl.sub.4
(g/hr) 2.22 2.22 Al.sub.2 Et.sub.3 Cl.sub.3 (g/hr) 17.0 17.0
Reactor Residence Time (sec) Before the 2nd feed point 4 -- Overall
35 40 Premixing Temperature (.degree.C.) 0 0 Premixing Time (sec) 6
6 Rate of Polymerization (g/hr) 487 401 Catalyst Efficiency (g
polymer/g VCl.sub.4 ) 219 181 (--Mw) 1.3 .times. 10.sup.5 1.0
.times. 10.sup.5 (--M.sub.z /--M.sub.w) 1.2 1.3 (--Mw/--Mn) 1.25
1.24 Composition (ethylene wt. %) Reactor sample taken right after
55.3 47.6 the 2nd feed point Final sample 45.4 41.0
______________________________________
EXAMPLE 4
The comparison in this example illustrates that narrow MWD EPM can
also be produced in a tubular reactor using the vanadium
oxytrichloride (VOCl.sub.3)-ethyl aluminum sesqui chloride
(Al.sub.2 Et.sub.3 Cl.sub.3) system when the conditions described
earlier are used. In example 4(B.) the catalyst components were
premixed in order to obtain rapid chain initiation. In example
4(A.) the polymerization conditions were the same, but the catalyst
components were fed separately to the reactor inlet. The
polymerization procedures of example 2(A.) and 2(B.) were repeated.
Table IV lists the run conditions.
The data in Table IV indicate that premixing of the catalyst
components produces narrow MWD polymers (M.sub.w /M.sub.n =1.8 and
M.sub.z /M.sub.w =1.5).
TABLE IV ______________________________________ Example Example 4A
4B ______________________________________ Reactor Inlet Temperature
(.degree.C.) 0 0 Reactor Outlet Temperature (.degree.C.) 7 12
Reactor Feed Rates Hexane (kg/hr) 60.2 61.1 Ethylene (kg/hr) 0.2
0.4 Propylene (kg/hr) 3.6 2.6 VOCl.sub.3 (g/hr) 1.73 5.07 Al.sub.2
Et.sub.3 Cl.sub.3 (g/hr) 7.44 54.2 Premixing Temperature
(.degree.C.) -- 10 Premixing Time (sec) -- 6 Reactor Residence Time
(sec) 52 37 Rate of Polymerization (g/hr) 685 359 Catalyst
Efficiency (g polymer/g VOCl.sub.3) 208 135 (--Mw) 2.8 .times.
10.sup.5 3.3 .times. 10.sup.5 (--M.sub.z /--M.sub.w) 2.7 1.5
(--Mw/--Mn) 2.7 1.8 Composition (ethylene wt. %) 40 49
______________________________________
EXAMPLE 5
This example illustrates that narrow MWD ethylene-propylene-diene
copolymers (EPDM) can be produced in a tubular reactor with
premixing of the catalyst components. The polymerization procedures
of example 2(B.) were repeated, except that a third monomer,
5-ethylidene-2-norbornene (ENB) was also used. The feed rates to
the reactor, premixing conditions, and the residence time for
example 5(A.) and 5(B.) are listed in Table V. Also shown in Table
V are the results of a control polymerization (5C) made in a
continuous flow stirred tank reactor.
The copolymer produced was recovered and analyzed by the procedures
described in Example 1 above. In addition, the ENB content was
determined by refractive index measurement (I. J. Gardner and G.
Ver Strate, Rubber Chem. Tech. 46, 1019 (1973)). The molecular
weight distribution, rate of polymerization and compositions are
shown in Table V.
The data listed in Table V clearly demonstrate that processes in
accordance with the present invention also result in very narrow
MWD for EPDM.
Sample 5(B.) and 5(C.), a polymer made in a continuous flow stirred
reactor with similar composition and molecular weight, were
compounded in the following formulation:
______________________________________ Polymer 100 High Abrasion
Furnace 80 Black (PHR) Oil (PHR) 50 ZnO (PHR) 2 Tetramethylthiuram
Di- 1 sulfide (PHR) 2-Mercaptobenzothiazole 0.5 (PHR) S (PHR) 1.5
______________________________________
The cured properties of these compounds are shown below:
______________________________________ 5B Control (5C)
______________________________________ Cure 160.degree. C./10'
Tensile 1334 1276 Elong. 570 550 100% Mod. 244 261 200% Mod. 412
435 300% Mod. 600 618 400% Mod. 840 841 500% Mod. 1160 1102 Shore A
78 80 Monsanto: 160.degree. C./60', l.degree. arc, 0-50
Range.sup.(a) (in-lb/dNm) ML.sup.(b) 2.8/3.2 4.0/4.5 MH.sup.(c)
37.2/42.0 35.0/39.6 ts2.sup.(d) 2.8 3.0 t'90.sup.(e) 22.2 18.5 Rate
7.9/8.9 5.9/6.7 ______________________________________ .sup.(a)
Monsanto Rheometer, Monsanto Company (Akron, OH) .sup.(b) ML = Cure
meter minimum torque; ASTM D208481 .sup.(c) MH = Cure meter maximum
torque; ASTM D208481 .sup.(d) ts2 = Time (in minutes) to 2point
rise above minimum torque; AST D208481 .sup.(e) t'90 = Time (in
minutes) to reach 90% of maximum torque rise above minimum; ASTM
D208481.
These data show that the cure rate of the narrow MWD polymer was
greater than that for the continuous flow stirred reactor control
polymer even though Mooney viscosity and ENB content were lower for
the former. Thus, the benefit of narrow MWD on cure rate is
shown.
TABLE V
__________________________________________________________________________
Examp1e 5A Examp1e 5B Example 5C
__________________________________________________________________________
Reactor Tubular Tubular Stirred Tank Reactor Inlet Temperature
(.degree.C.) 0 -20 Reactor Outlet Temperature (.degree.C.) 20 -10
Reactor Feed Rates Heaxane (kg/hr) 60.9 60.9 Ethylene (kg/hr) 0.65
0.20 Propylane (kg/hr) 5.5 2.15 Diene (kg/hr) 0.036 0.026 VCl.sub.4
(g/hr) 5.24 2.22 Al.sub.2 Et.sub.3 Cl.sub.3 (g/hr) 40.4 21.4
Catalyst Premixing Temperature (.degree.C.) 0 -20 Catslyst
Premixing Time (sec) 6 10 Reactor Residenece Time (sec) 30 48 Rate
of Polymerization (g/hr) 1479 454 Catalyst Efficiency (g polymer/g
VCl.sub.4) 282 205 (--Mw) 1.3 .times. 10.sup.5 1.2 .times. 10.sup.5
1.6 (--M.sub.z /--M.sub.w) 1.37 1.30 4. (--Mw/--Mn) 1.44 1.61 4.
Mooney Viscosity ML (1 + 8) 1OO.degree. C. 45 51 55 Composition
Ethylene wt. % 39.3 39.3 49. ENB wt. % 3.5 4.2 4.5 Cure Rate (dNm)
-- 8.9 6.7
__________________________________________________________________________
EXAMPLE 6
This example illustrates that narrow MWD EPM can be produced in a
tubular reactor with a different configuration when the critical
process conditions in accordance with the present invention are
used. The polymerization reactor consisted of 12 meters of a 3/8"
tubing. The experimental procedures of example 2(B.) were repeated.
The process conditions are listed in Table VI.
Data listed in Table VI show that this tubular reactor produced
polymer with an MWD as narrow as that of polymers made in the 1"
pipe used in the previous example.
TABLE VI ______________________________________ Reactor Inlet
Temperature (.degree.C.) -1 Reactor Outlet Temperature (.degree.C.)
30 Reactor Feed Rates Hexane (kg/hr) 31.1 Ethylene (kg/hr) 0.7
Propylene (kg/hr) 11 VCl.sub.4 (g/hr) 8.27 Al.sub.2 Et.sub.3
Cl.sub.3 (g/hr) 58.5 Reactor Residence Time (sec) 45 Catalyst
Premixing Temperature (.degree.C.) 10 Catalyst Premixing Time (sec)
6 Rate of Polymerization (g/hr) 1832 Catalyst Efficiency (g
polymer/g VCl.sub.4) 222 (--Mw) 1.4 .times. 10.sup.5 (--M.sub.z
/--M.sub.w) 1.4 (--Mw/--Mn) 1.5 Composition (ethylene wt. %) 38
______________________________________
EXAMPLES 7-10
In these examples, polymers made as described in the previous
examples were dissolved in lubricating oil basestock and the
viscosity effects were evaluated. The narrow MWD and intramolecular
compositional distribution of these polymers provide improvements
in MRV (Mini Rotary Viscosity) and SSI (Shear Stability Index).
MRV: This is a viscosity measurement in centipoises (cps) at
-25.degree. C. according to ASTM-D 3829 using the Mini-Rotary
Viscometer and is an industry accepted evaluation for the low
temperature pumpability of a lubricating oil.
T.E.: This represents Thickening Efficiency and is defined as the
ratio of the weight percent of a polyisobutylene (sold as an oil
solution by Exxon Chemical Company as Paratone N), having a
Staudinger molecular weight of 20,000, required to thicken a
solvent-extracted neutral mineral lubricating oil, having a
viscosity of 150 SUS at 37.8.degree. C., a viscosity index of 105
and an ASTM pour point of 0.degree. F., (Solvent 150 Neutral) to a
viscosity of 12.3 centistokes at 98.9.degree. C., to the weight
percent of a test copolymer required to thicken the same oil to the
same viscosity at the same temperature.
SSI: This value is Shear Stability Index and measures the stability
of polymers used as V.I. improvers in motor oils subjected to high
shear rates. In this method the sample under test is blended with a
typical basestock to a viscosity increase at 210.degree. F. of
7.0.+-.5 centistokes. Two portions of the blend are successively
subjected to sonic shearing forces at a specific power input and a
constant temperature for 15 minutes. Viscosities are determined on
the blends both before and after the treatment; the decrease in
viscosity after the treatment is a measure of the molecular
breakdown of the polymer under test. A series of standard samples
is used as a reference to establish the correct value for the
sample under test. The corrected value is reported as the SSI which
is the percent sonic breakdown to the nearest 1%.
In these tests, a Raytheon Model DF 101, 200 watt, 10 kilocycle
sonic oscillator was used, the temperature was 37 .+-.4.degree. C.,
power input is 0.75 ampere, time of test is 15.0 minutes .+-.10
seconds.
EXAMPLE 7
In this example, polymers made as described in Example 1 and 2 were
dissolved in lubricating oil to provide a kinematic viscosity of
13.5 centistokes at 100.degree. C. (ASTM D445) SSI was measured in
Solvent 150 Neutral basestock (31 cS. min at 100.degree. F., pour
point of 50.degree. F. and broad wax distribution). MRV was
measured in a Mid-Continent basestock being a mixture of Solvent
100 Neutral (20 cS. Min at 100.degree. F.) and Solvent 250 Neutral
(55 cS min. at 100.degree. F.) and having a narrow (C.sub.24
-C.sub.36) wax distribution and containing 0.2 wt % vinyl acetate
fumarate pour depressant (Paraflow 449, Exxon Chemical Co.)
Results are tabulated below:
______________________________________ Oil Containing Shear
Stability Pumpability Copolymer as Ethylene Thickening SSI MRV @
Described In: wt % Efficiency % Loss -25.degree. C. cps
______________________________________ Example 1 42 2.8 28 32,500
Example 2A 42 3.6 44 270,000 Example 2B 39 2.7 18 25,000 Example 2C
41 2.06 8 20,000 ______________________________________
These data clearly show the improvements in SSI and MRV possible
with the polymers of the present invention. Example 2B outperformed
Example 1 in SSI at the same TE. Both Examples 2B and 2C, made with
premixed catalyst, outperformed Example 1 (made as in Ex. 1) from
the backmixed reactor, and Example 2A, made with no premixing and
having the broad inter CD.
EXAMPLE 8
In this example it is shown that the polymer of Example 3, which
was made with multiple ethylene feeds and which retained its narrow
MWD even with a second ethylene feed, has good shear stability.
______________________________________ Sample TE SSI % Loss
______________________________________ Example 2B 2.7 18 Example 3B
2.6 14.5 ______________________________________
The shear stability of 3B was equivalent to the polymer made with
the single feed. Thus, it is possible to tailor compositional
distribution without significantly affecting MWD and SSI.
EXAMPLE 9
In this example it is shown that the premixing of the VOCl.sub.3
catalyst components of Example 4, which effected a narrowing of
MWD, permits a much higher TE polymer to be employed with the same
SSI, as shown in Table 9.
TABLE 9 ______________________________________ Sample TE SSI % Loss
______________________________________ Example 4A 3.8 52 Example 4B
4.9 53 ______________________________________
It should be noted, however, that a polymer of the same TE as the
polymer of Example 4A, when made with premixing exhibits much
better SSI than the Example 4A.
EXAMPLE 10
This example demonstrates a terpolymer in accordance with this
invention exhibits the same viscosity improvements. A terpolymer
sample was prepared as in Example 5(A). This sample was tested for
SSI and MRV. Sample analysis and results appear in Table 10.
TABLE 10 ______________________________________ Ethylene SSI,
Sample wt % ENB wt % TE MRV % Loss
______________________________________ Example 10A 39.3 3.5 2.5
33,000 29 ______________________________________
* * * * *